From 7b546116fe06554f8bf03c8d5ac2436877eceeee Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl@microsoft.com>
Date: Fri, 18 Dec 2020 17:34:04 -0800
Subject: [PATCH 01/14] Download and extract PSTools.zip.

---
 azure-devops/provision-image.ps1 | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/azure-devops/provision-image.ps1 b/azure-devops/provision-image.ps1
index ba9e940c575..77b2f24aaad 100644
--- a/azure-devops/provision-image.ps1
+++ b/azure-devops/provision-image.ps1
@@ -56,9 +56,18 @@ if ([string]::IsNullOrEmpty($AdminUserPassword)) {
   Start-Transcript -Path $TranscriptPath
 } else {
   Write-Host 'AdminUser password supplied; switching to AdminUser.'
-  $PsExecPath = Get-TempFilePath -Extension 'exe'
-  Write-Host "Downloading psexec to: $PsExecPath"
-  & curl.exe -L -o $PsExecPath -s -S https://live.sysinternals.com/PsExec64.exe
+
+  # https://docs.microsoft.com/en-us/sysinternals/downloads/psexec
+  $PsToolsZipUrl = 'https://download.sysinternals.com/files/PSTools.zip'
+  $PsToolsZipPath = Get-TempFilePath -Extension 'PSTools.zip'
+  Write-Host "Downloading $PsToolsZipUrl to: $PsToolsZipPath"
+  & curl.exe -L -o $PsToolsZipPath -s -S $PsToolsZipUrl
+
+  $TempSubdirPath = Get-TempFilePath -Extension 'dir'
+  Write-Host "Extracting $PsToolsZipPath to: $TempSubdirPath"
+  Expand-Archive -Path $PsToolsZipPath -DestinationPath $TempSubdirPath -Force
+  $PsExecPath = Join-Path $TempSubdirPath 'PsExec64.exe'
+
   $PsExecArgs = @(
     '-u',
     'AdminUser',

From ee065353ef8a733b2c14510ecbea9d3064a04df2 Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl@microsoft.com>
Date: Fri, 18 Dec 2020 18:47:19 -0800
Subject: [PATCH 02/14] SuppressAzurePowerShellBreakingChangeWarnings.

---
 azure-devops/create-vmss.ps1 | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/azure-devops/create-vmss.ps1 b/azure-devops/create-vmss.ps1
index 1434ce0ac48..963fb7f874a 100644
--- a/azure-devops/create-vmss.ps1
+++ b/azure-devops/create-vmss.ps1
@@ -17,6 +17,9 @@ or are running from Azure Cloud Shell.
 
 $ErrorActionPreference = 'Stop'
 
+# https://aka.ms/azps-changewarnings
+$Env:SuppressAzurePowerShellBreakingChangeWarnings = 'true'
+
 $Location = 'westus2'
 $Prefix = 'StlBuild-' + (Get-Date -Format 'yyyy-MM-dd')
 $VMSize = 'Standard_D32as_v4'

From 220ed547160325f37f7ea76a3642cd4ab2f130ed Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl@microsoft.com>
Date: Fri, 18 Dec 2020 19:33:47 -0800
Subject: [PATCH 03/14] Refactor with DownloadAndExtractZip.

---
 azure-devops/provision-image.ps1 | 40 +++++++++++++++++++++++++-------
 1 file changed, 32 insertions(+), 8 deletions(-)

diff --git a/azure-devops/provision-image.ps1 b/azure-devops/provision-image.ps1
index 77b2f24aaad..308af7d7f65 100644
--- a/azure-devops/provision-image.ps1
+++ b/azure-devops/provision-image.ps1
@@ -50,6 +50,36 @@ Function Get-TempFilePath {
   return Join-Path $tempPath $tempName
 }
 
+<#
+.SYNOPSIS
+Downloads and extracts a ZIP file to a newly created temporary subdirectory.
+
+.DESCRIPTION
+DownloadAndExtractZip returns a path containing the extracted contents.
+
+.PARAMETER Url
+The URL of the ZIP file to download.
+#>
+Function DownloadAndExtractZip {
+  Param(
+    [String]$Url
+  )
+
+  if ([String]::IsNullOrWhiteSpace($Url)) {
+    throw 'Missing Url'
+  }
+
+  $ZipPath = Get-TempFilePath -Extension 'zip'
+  Write-Host "Downloading $Url to: $ZipPath"
+  & curl.exe -L -o $ZipPath -s -S $Url
+
+  $TempSubdirPath = Get-TempFilePath -Extension 'dir'
+  Write-Host "Extracting $ZipPath to: $TempSubdirPath"
+  Expand-Archive -Path $ZipPath -DestinationPath $TempSubdirPath -Force
+
+  return $TempSubdirPath
+}
+
 $TranscriptPath = 'C:\provision-image-transcript.txt'
 
 if ([string]::IsNullOrEmpty($AdminUserPassword)) {
@@ -59,14 +89,8 @@ if ([string]::IsNullOrEmpty($AdminUserPassword)) {
 
   # https://docs.microsoft.com/en-us/sysinternals/downloads/psexec
   $PsToolsZipUrl = 'https://download.sysinternals.com/files/PSTools.zip'
-  $PsToolsZipPath = Get-TempFilePath -Extension 'PSTools.zip'
-  Write-Host "Downloading $PsToolsZipUrl to: $PsToolsZipPath"
-  & curl.exe -L -o $PsToolsZipPath -s -S $PsToolsZipUrl
-
-  $TempSubdirPath = Get-TempFilePath -Extension 'dir'
-  Write-Host "Extracting $PsToolsZipPath to: $TempSubdirPath"
-  Expand-Archive -Path $PsToolsZipPath -DestinationPath $TempSubdirPath -Force
-  $PsExecPath = Join-Path $TempSubdirPath 'PsExec64.exe'
+  $ExtractedPsToolsPath = DownloadAndExtractZip -Url $PsToolsZipUrl
+  $PsExecPath = Join-Path $ExtractedPsToolsPath 'PsExec64.exe'
 
   $PsExecArgs = @(
     '-u',

From 3ef1f355661290436d13b73f65553ce883ccb4f3 Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl@microsoft.com>
Date: Fri, 18 Dec 2020 20:00:19 -0800
Subject: [PATCH 04/14] Use PowerShell 7.1.0 for UseMinimalHeader, cleanup
 extracted directories.

---
 azure-devops/provision-image.ps1 | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/azure-devops/provision-image.ps1 b/azure-devops/provision-image.ps1
index 308af7d7f65..448e056747a 100644
--- a/azure-devops/provision-image.ps1
+++ b/azure-devops/provision-image.ps1
@@ -83,7 +83,7 @@ Function DownloadAndExtractZip {
 $TranscriptPath = 'C:\provision-image-transcript.txt'
 
 if ([string]::IsNullOrEmpty($AdminUserPassword)) {
-  Start-Transcript -Path $TranscriptPath
+  Start-Transcript -Path $TranscriptPath -UseMinimalHeader
 } else {
   Write-Host 'AdminUser password supplied; switching to AdminUser.'
 
@@ -92,6 +92,11 @@ if ([string]::IsNullOrEmpty($AdminUserPassword)) {
   $ExtractedPsToolsPath = DownloadAndExtractZip -Url $PsToolsZipUrl
   $PsExecPath = Join-Path $ExtractedPsToolsPath 'PsExec64.exe'
 
+  # https://github.com/PowerShell/PowerShell/releases/latest
+  $PowerShellZipUrl = 'https://github.com/PowerShell/PowerShell/releases/download/v7.1.0/PowerShell-7.1.0-win-x64.zip'
+  $ExtractedPowerShellPath = DownloadAndExtractZip -Url $PowerShellZipUrl
+  $PwshPath = Join-Path $ExtractedPowerShellPath 'pwsh.exe'
+
   $PsExecArgs = @(
     '-u',
     'AdminUser',
@@ -99,7 +104,7 @@ if ([string]::IsNullOrEmpty($AdminUserPassword)) {
     $AdminUserPassword,
     '-accepteula',
     '-h',
-    'C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe',
+    $PwshPath,
     '-ExecutionPolicy',
     'Unrestricted',
     '-File',
@@ -112,7 +117,8 @@ if ([string]::IsNullOrEmpty($AdminUserPassword)) {
   Write-Host 'Reading transcript...'
   Get-Content -Path $TranscriptPath
   Write-Host 'Cleaning up...'
-  Remove-Item $PsExecPath
+  Remove-Item -Recurse -Path $ExtractedPsToolsPath
+  Remove-Item -Recurse -Path $ExtractedPowerShellPath
   exit $proc.ExitCode
 }
 

From 2dbe859c8e2acbff94561a2fbbc39a262696fbf0 Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl@microsoft.com>
Date: Fri, 18 Dec 2020 20:26:08 -0800
Subject: [PATCH 05/14] Redact the AdminUserPassword.

---
 azure-devops/provision-image.ps1 | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/azure-devops/provision-image.ps1 b/azure-devops/provision-image.ps1
index 448e056747a..38bce3a5262 100644
--- a/azure-devops/provision-image.ps1
+++ b/azure-devops/provision-image.ps1
@@ -101,7 +101,7 @@ if ([string]::IsNullOrEmpty($AdminUserPassword)) {
     '-u',
     'AdminUser',
     '-p',
-    $AdminUserPassword,
+    'AdminUserPassword_REDACTED',
     '-accepteula',
     '-h',
     $PwshPath,
@@ -110,8 +110,8 @@ if ([string]::IsNullOrEmpty($AdminUserPassword)) {
     '-File',
     $PSCommandPath
   )
-
   Write-Host "Executing: $PsExecPath $PsExecArgs"
+  $PsExecArgs[3] = $AdminUserPassword
 
   $proc = Start-Process -FilePath $PsExecPath -ArgumentList $PsExecArgs -Wait -PassThru
   Write-Host 'Reading transcript...'

From 19c4e34c082cdacfba269f44143bbc50b8e08f2a Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl@microsoft.com>
Date: Fri, 18 Dec 2020 20:28:39 -0800
Subject: [PATCH 06/14] Simplify download logging.

---
 azure-devops/provision-image.ps1 | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/azure-devops/provision-image.ps1 b/azure-devops/provision-image.ps1
index 38bce3a5262..a28c8d48f3f 100644
--- a/azure-devops/provision-image.ps1
+++ b/azure-devops/provision-image.ps1
@@ -70,11 +70,8 @@ Function DownloadAndExtractZip {
   }
 
   $ZipPath = Get-TempFilePath -Extension 'zip'
-  Write-Host "Downloading $Url to: $ZipPath"
   & curl.exe -L -o $ZipPath -s -S $Url
-
   $TempSubdirPath = Get-TempFilePath -Extension 'dir'
-  Write-Host "Extracting $ZipPath to: $TempSubdirPath"
   Expand-Archive -Path $ZipPath -DestinationPath $TempSubdirPath -Force
 
   return $TempSubdirPath
@@ -89,11 +86,13 @@ if ([string]::IsNullOrEmpty($AdminUserPassword)) {
 
   # https://docs.microsoft.com/en-us/sysinternals/downloads/psexec
   $PsToolsZipUrl = 'https://download.sysinternals.com/files/PSTools.zip'
+  Write-Host "Downloading: $PsToolsZipUrl"
   $ExtractedPsToolsPath = DownloadAndExtractZip -Url $PsToolsZipUrl
   $PsExecPath = Join-Path $ExtractedPsToolsPath 'PsExec64.exe'
 
   # https://github.com/PowerShell/PowerShell/releases/latest
   $PowerShellZipUrl = 'https://github.com/PowerShell/PowerShell/releases/download/v7.1.0/PowerShell-7.1.0-win-x64.zip'
+  Write-Host "Downloading: $PowerShellZipUrl"
   $ExtractedPowerShellPath = DownloadAndExtractZip -Url $PowerShellZipUrl
   $PwshPath = Join-Path $ExtractedPowerShellPath 'pwsh.exe'
 

From 59c75e7e772abc1d0f1714dd0e83d8af2413b176 Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl@microsoft.com>
Date: Tue, 5 Jan 2021 17:55:48 -0800
Subject: [PATCH 07/14] Python 3.9.1.

---
 azure-devops/provision-image.ps1 | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/azure-devops/provision-image.ps1 b/azure-devops/provision-image.ps1
index a28c8d48f3f..2ef68ebda9b 100644
--- a/azure-devops/provision-image.ps1
+++ b/azure-devops/provision-image.ps1
@@ -138,7 +138,7 @@ $Workloads = @(
 $ReleaseInPath = 'Preview'
 $Sku = 'Enterprise'
 $VisualStudioBootstrapperUrl = 'https://aka.ms/vs/16/pre/vs_enterprise.exe'
-$PythonUrl = 'https://www.python.org/ftp/python/3.9.0/python-3.9.0-amd64.exe'
+$PythonUrl = 'https://www.python.org/ftp/python/3.9.1/python-3.9.1-amd64.exe'
 
 # https://docs.microsoft.com/en-us/windows-hardware/drivers/download-the-wdk
 $WindowsDriverKitUrl = 'https://go.microsoft.com/fwlink/?linkid=2128854'

From 5d8c059b8a46c415ea8d1e81e85c82470b2440c2 Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl@microsoft.com>
Date: Wed, 20 Jan 2021 16:12:16 -0800
Subject: [PATCH 08/14] PowerShell 7.1.1.

---
 azure-devops/provision-image.ps1 | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/azure-devops/provision-image.ps1 b/azure-devops/provision-image.ps1
index 2ef68ebda9b..240a875291b 100644
--- a/azure-devops/provision-image.ps1
+++ b/azure-devops/provision-image.ps1
@@ -91,7 +91,7 @@ if ([string]::IsNullOrEmpty($AdminUserPassword)) {
   $PsExecPath = Join-Path $ExtractedPsToolsPath 'PsExec64.exe'
 
   # https://github.com/PowerShell/PowerShell/releases/latest
-  $PowerShellZipUrl = 'https://github.com/PowerShell/PowerShell/releases/download/v7.1.0/PowerShell-7.1.0-win-x64.zip'
+  $PowerShellZipUrl = 'https://github.com/PowerShell/PowerShell/releases/download/v7.1.1/PowerShell-7.1.1-win-x64.zip'
   Write-Host "Downloading: $PowerShellZipUrl"
   $ExtractedPowerShellPath = DownloadAndExtractZip -Url $PowerShellZipUrl
   $PwshPath = Join-Path $ExtractedPowerShellPath 'pwsh.exe'

From 858829950512c6af9f2dc41b81d9e0e7990618d5 Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl@microsoft.com>
Date: Wed, 20 Jan 2021 16:39:38 -0800
Subject: [PATCH 09/14] Enable test-signed kernel-mode drivers.

---
 azure-devops/provision-image.ps1 | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/azure-devops/provision-image.ps1 b/azure-devops/provision-image.ps1
index 240a875291b..7bd53a0ece7 100644
--- a/azure-devops/provision-image.ps1
+++ b/azure-devops/provision-image.ps1
@@ -396,3 +396,9 @@ Write-Host 'Finished updating PATH!'
 
 PipInstall pip
 PipInstall psutil
+
+# https://docs.microsoft.com/en-us/windows-hardware/drivers/devtest/bcdedit--set#verification-settings
+Write-Host 'Enabling test-signed kernel-mode drivers...'
+bcdedit /set testsigning on
+
+Write-Host 'Done!'

From fecd705dfece519b8fb43c3a3f911e9aaa8a7f4b Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl@microsoft.com>
Date: Wed, 20 Jan 2021 17:37:05 -0800
Subject: [PATCH 10/14] Work around VSO-1268140.

VSO-1268140 "EDG: weirdness evaluating rvalue-qualified constexpr member function"
---
 tests/std/tests/P0220R1_optional/test.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tests/std/tests/P0220R1_optional/test.cpp b/tests/std/tests/P0220R1_optional/test.cpp
index a7bb292e541..ec0b2904315 100644
--- a/tests/std/tests/P0220R1_optional/test.cpp
+++ b/tests/std/tests/P0220R1_optional/test.cpp
@@ -5495,13 +5495,17 @@ constexpr int test()
     {
         optional<X> opt(in_place, 2);
         Y y(3);
+#ifndef __EDG__ // TRANSITION, VSO-1268140
         assert(std::move(opt).value_or(y) == 2);
         assert(*opt == 0);
+#endif // ^^^ no workaround ^^^
     }
     {
         optional<X> opt(in_place, 2);
+#ifndef __EDG__ // TRANSITION, VSO-1268140
         assert(std::move(opt).value_or(Y(3)) == 2);
         assert(*opt == 0);
+#endif // ^^^ no workaround ^^^
     }
     {
         optional<X> opt;

From 166cfbf04e5f1c808c149d3d65fd1c532c882803 Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl@microsoft.com>
Date: Wed, 20 Jan 2021 19:44:32 -0800
Subject: [PATCH 11/14] PsExec now requires `-i` when using `-h`.

---
 azure-devops/provision-image.ps1 | 1 +
 1 file changed, 1 insertion(+)

diff --git a/azure-devops/provision-image.ps1 b/azure-devops/provision-image.ps1
index 7bd53a0ece7..238f6effecf 100644
--- a/azure-devops/provision-image.ps1
+++ b/azure-devops/provision-image.ps1
@@ -102,6 +102,7 @@ if ([string]::IsNullOrEmpty($AdminUserPassword)) {
     '-p',
     'AdminUserPassword_REDACTED',
     '-accepteula',
+    '-i',
     '-h',
     $PwshPath,
     '-ExecutionPolicy',

From 94a9a5c5e89c75738dae5b17cf506519657cb476 Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl@microsoft.com>
Date: Wed, 20 Jan 2021 21:18:34 -0800
Subject: [PATCH 12/14] Run `pip install` with `--progress-bar off`.

---
 azure-devops/provision-image.ps1 | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/azure-devops/provision-image.ps1 b/azure-devops/provision-image.ps1
index 238f6effecf..8468b850ad6 100644
--- a/azure-devops/provision-image.ps1
+++ b/azure-devops/provision-image.ps1
@@ -354,7 +354,7 @@ Function PipInstall {
 
   try {
     Write-Host "Installing or upgrading $Package..."
-    python.exe -m pip install --upgrade $Package
+    python.exe -m pip install --progress-bar off --upgrade $Package
     Write-Host "Done installing or upgrading $Package."
   }
   catch {

From d0dbb21e95a05174aeae49c9d2aa9e6b0ccd1cf0 Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl@microsoft.com>
Date: Wed, 20 Jan 2021 21:35:21 -0800
Subject: [PATCH 13/14] Use the new VMSS pool.

---
 azure-pipelines.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/azure-pipelines.yml b/azure-pipelines.yml
index 3fa907668b9..f342d73784b 100644
--- a/azure-pipelines.yml
+++ b/azure-pipelines.yml
@@ -6,7 +6,7 @@
 variables:
   tmpDir: 'D:\Temp'
 
-pool: 'StlBuild-2020-12-08-1'
+pool: 'StlBuild-2021-01-20-2'
 
 stages:
   - stage: Code_Format

From a23f19ff3fc31a87898c95408e2fb5198af295c3 Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl@microsoft.com>
Date: Wed, 20 Jan 2021 21:35:51 -0800
Subject: [PATCH 14/14] Update VS, CMake, Ninja, Python versions.

---
 CMakeLists.txt |  2 +-
 README.md      | 10 +++++-----
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1e712f36ad8..8b166a3d5a2 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -5,7 +5,7 @@ if (NOT DEFINED CMAKE_TOOLCHAIN_FILE AND EXISTS "${CMAKE_CURRENT_LIST_DIR}/vcpkg
     set(CMAKE_TOOLCHAIN_FILE "${CMAKE_CURRENT_LIST_DIR}/vcpkg/scripts/buildsystems/vcpkg.cmake")
 endif()
 
-cmake_minimum_required(VERSION 3.18)
+cmake_minimum_required(VERSION 3.19)
 set(CMAKE_TRY_COMPILE_TARGET_TYPE STATIC_LIBRARY)
 project(msvc_standard_libraries LANGUAGES CXX)
 
diff --git a/README.md b/README.md
index 570e9cedcf9..40546698950 100644
--- a/README.md
+++ b/README.md
@@ -143,10 +143,10 @@ Just try to follow these rules, so we can spend more time fixing bugs and implem
 The STL uses boost-math headers to provide P0226R1 Mathematical Special Functions. We recommend using [vcpkg][] to
 acquire this dependency.
 
-1. Install Visual Studio 2019 16.9 Preview 2 or later.
+1. Install Visual Studio 2019 16.9 Preview 3 or later.
     * We recommend selecting "C++ CMake tools for Windows" in the VS Installer.
     This will ensure that you're using supported versions of CMake and Ninja.
-    * Otherwise, install [CMake][] 3.18 or later, and [Ninja][] 1.8.2 or later.
+    * Otherwise, install [CMake][] 3.19 or later, and [Ninja][] 1.10.2 or later.
 2. Open Visual Studio, and choose the "Clone or check out code" option. Enter the URL of this repository,
    `https://github.com/microsoft/STL`.
 3. Open a terminal in the IDE with `` Ctrl + ` `` (by default) or press on "View" in the top bar, and then "Terminal".
@@ -158,10 +158,10 @@ acquire this dependency.
 
 # How To Build With A Native Tools Command Prompt
 
-1. Install Visual Studio 2019 16.9 Preview 2 or later.
+1. Install Visual Studio 2019 16.9 Preview 3 or later.
     * We recommend selecting "C++ CMake tools for Windows" in the VS Installer.
     This will ensure that you're using supported versions of CMake and Ninja.
-    * Otherwise, install [CMake][] 3.18 or later, and [Ninja][] 1.8.2 or later.
+    * Otherwise, install [CMake][] 3.19 or later, and [Ninja][] 1.10.2 or later.
 2. Open a command prompt.
 3. Change directories to a location where you'd like a clone of this STL repository.
 4. `git clone https://github.com/microsoft/STL`
@@ -234,7 +234,7 @@ C:\Users\username\Desktop>dumpbin /IMPORTS .\example.exe | findstr msvcp
 # How To Run The Tests With A Native Tools Command Prompt
 
 1. Follow either [How To Build With A Native Tools Command Prompt][] or [How To Build With The Visual Studio IDE][].
-2. Acquire [Python][] 3.9 or newer and have it on the `PATH` (or run it directly using its absolute or relative path).
+2. Acquire [Python][] 3.9.1 or newer and have it on the `PATH` (or run it directly using its absolute or relative path).
 3. Have LLVM's `bin` directory on the `PATH` (so `clang-cl.exe` is available).
     * We recommend selecting "C++ Clang tools for Windows" in the VS Installer. This will automatically add LLVM to the
     `PATH` of the x86 and x64 Native Tools Command Prompts, and will ensure that you're using a supported version.