ci: fix explanation why LLVM download is disabled for windows-gnu

[mati865]

Continuation of #132781

[rustbot]

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[mati865]

Basically my plan is to do try build with dist so the artifacts get uploaded and then do another try but with test jobs.
If that fails, I think we should merge dist builders change only and then in later PR do the same for test jobs.

[Kobzol]

I would personally prefer to disable LLVM download on the dist runners, to exercise the LLVM build path regularly.

[mati865]

I think dist runners always build LLVM artifacts for download (at least that appears to be the case in #132781) despite using the same environment variable.
Even if that's not the case, changing it would be a bigger change that affects all platforms.

[Kobzol]

Yeah, just to clarify, what I meant was that we shouldn't change the behavior on dist runners - they should always build.

[Mark-Simulacrum]

@bors r+ rollup=never

[bors]

📌 Commit 81f25bb has been approved by Mark-Simulacrum

It is now in the queue for this repository.

[Kobzol]

FWIW, this PR currently still enables LLVM download for the dist- builders. Not sure if that works, or if we even want to enable that.

[Mark-Simulacrum]

Does it actually do that? AFAICT, the NO_DOWNLOAD_CI_LLVM there was just a no-op -- we don't ever read that outside of non-dist builds afaict (

rust/src/ci/run.sh

Lines 165 to 185 in 481b5fa

	# We enable this for non-dist builders, since those aren't trying to produce
	# fresh binaries. We currently don't entirely support distributing a fresh
	# copy of the compiler (including llvm tools, etc.) if we haven't actually
	# built LLVM, since not everything necessary is copied into the
	# local-usage-only LLVM artifacts. If that changes, this could maybe be made
	# true for all builds. In practice it's probably a good idea to keep building
	# LLVM continuously on at least some builders to ensure it works, though.
	# (And PGO is its own can of worms).
	if [ "$NO_DOWNLOAD_CI_LLVM"="" ];then
	RUST_CONFIGURE_ARGS="$RUST_CONFIGURE_ARGS --set llvm.download-ci-llvm=if-unchanged"
	else
	# CI rustc requires CI LLVM to be enabled (see https://github.com/rust-lang/rust/issues/123586).
	NO_DOWNLOAD_CI_RUSTC=1
	# When building for CI we want to use the static C++ Standard library
	# included with LLVM, since a dynamic libstdcpp may not be available.
	RUST_CONFIGURE_ARGS="$RUST_CONFIGURE_ARGS --set llvm.static-libstdcpp"
	fi
	if [ "$NO_DOWNLOAD_CI_RUSTC"="" ];then
	RUST_CONFIGURE_ARGS="$RUST_CONFIGURE_ARGS --set rust.download-rustc=if-unchanged"
	fi

is all outside DEPLOY=1)

@bors r- until we settle this

[Kobzol]

Sorry, you're right, I missed this, the bash scripts are a bit confusing. Then this should be fine.

[Mark-Simulacrum]

@bors r+

[bors]

📌 Commit 81f25bb has been approved by Mark-Simulacrum

It is now in the queue for this repository.

[bors]

⌛ Testing commit 81f25bb with merge 4fde74c...

[bors]

💔 Test failed - checks-actions

[Mark-Simulacrum]

@rustbot author

Seems probably real?

[mati865]

Retitled PR and commit to make it reflect the true change. The previous title would give a false hope for CI time improvements.

[mati865]

@Kobzol may I ask you for reapproval? Thank you in advance.

[Kobzol]

Huh, this should have been approved already. I didn't notice the force push.

@bors r+

[bors]

📌 Commit b20bc53 has been approved by Kobzol

It is now in the queue for this repository.