perform sanity checks before initiating cross-compilation in MirOpt

[onur-ozkan]

from #115130

Fix the bootstrap santity check to also check for the relevant cross compilation target(s) when --bless is used

This PR fixes that.

[rustbot]

r? @albertlarsan68

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[Noratrieb]

does this mean that running MIR opt tests, even just for the host, always fails if the cross compilation toolchain isn't installed?

[onur-ozkan]

Even just for the host, MirOpt test with --bless flag fails due to missing toolchain.

[Noratrieb]

can we fix that? i would very much like to be able to test the host while ignoring the cross compilation, with a big warning

[onur-ozkan]

Sure I can do that. Good idea.

@rustbot author

[onur-ozkan]

rust/src/bootstrap/src/core/build_steps/test.rs

Lines 1492 to 1495 in 27794f9

	// We use custom logic to bless the mir-opt suite: mir-opt tests have multiple variants
	// (32bit vs 64bit, and panic=abort vs panic=unwind), and all of them needs to be blessed.
	// When blessing, we try best-effort to also bless the other variants, to aid developers.
	if builder.config.cmd.bless() {

Hmm, I need to be sure if blessing will continue working as expected when skipping the cross-target.

cc @pietroalbini

[bors]

☔ The latest upstream changes (presumably #120060) made this pull request unmergeable. Please resolve the merge conflicts.

[saethlin]

I think this PR is no longer required since #120060 ? Buildling MIR-only sysroots is intended to obviate needing these checks.

[onur-ozkan]

I think this PR is no longer required since #120060 ? Buildling MIR-only sysroots is intended to obviate needing these checks.

Yes, this is no longer needed. Thank you!