Sporadic CI failure in vcpkg checkout

[StephanTLavavej]

The CI run 20210202.19 for #1605 failed on one machine, in the "Checkout vcpkg source" step, with:

Starting: Checkout vcpkg source
==============================================================================
Task         : Command line
Description  : Run a command line script using Bash on Linux and macOS and cmd.exe on Windows
Version      : 2.178.0
Author       : Microsoft Corporation
Help         : https://docs.microsoft.com/azure/devops/pipelines/tasks/utility/command-line
==============================================================================
Generating script.
========================== Starting Command Output ===========================
"C:\windows\system32\cmd.exe" /D /E:ON /V:OFF /S /C "CALL "C:\a\_temp\f994189d-4253-4eb8-be96-50a3ed3a6caf.cmd""
https://github.com/Microsoft/vcpkg.git
error: bad signature 0x00000000
fatal: index file corrupt
error: bad signature 0x00000000
fatal: index file corrupt
##[error]Cmd.exe exited with code '128'.
Finishing: Checkout vcpkg source

I believe this is the first time I've encountered this, but Curtis J Bezault (@cbezault) has seen this before. We don't know what's causing this.

[StephanTLavavej]

vcpkg has been removed by #2151. Closing this - we can file a new issue if we see llvm-project or boost-math checkout failures.