Avoid trusting bootstrap for git-hash availability for the version-verbose-commit-hash test

[jieyouxu]

Caution

Blocked on:

1. ci.py rewrite: Rewrite the ci.py script in Rust #136864
2. Rebasing then setting COMPILETEST_HAS_GIT_HASH=1 when under CI conditions.

Summary

• Instead of trusting git hash availability reported by bootstrap, we need to bypass bootstrap and directly work with CI to determine whether git hash should be available and run the tests/run-make/version-verbose-commit-hash test.
• This is to catch regressions like Recent pre-nightly builds have "commit-hash: unknown" in their version info #132845 where the regression slip through because bootstrap's git-hash logic was broken, where bootstrap reported git-hash was available but actually produced {rustc,rustdoc} that had omitted git hash info.

Testing

Manually tested locally:

• COMPILETEST_HAS_GIT_HASH=1 ./x test tests/run-make/version-verbose-commit-hash with compiler profile + rust.channel defaulted to dev causes test to fail because no git hash info.
• COMPILETEST_HAS_GIT_HASH=1 ./x test tests/run-make/version-verbose-commit-hash with compiler profile + rust.channel=nightly passes test.

Review advice

• Should double-check if COMPILETEST_HAS_GIT_HASH=1 is correctly set in CI.
• Please do let me know if there's a better scheme to handle this.

Fixes #132875.

[rustbot]

r? @onur-ozkan

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[jieyouxu]

@rustbot blocked (#136864)

[jieyouxu]

I'll rethink this approach.