[libc-commits] [libc] [libc] Properly clear out errno in tests that check its value. (PR #131650)

[Michael Jones via libc-commits]

https://github.com/michaelrj-google commented:

adding an `ErrnoCheckingTest` seems good as long as it doesn't overlap with the fenv tests. I don't see any cases where it would from a quick glance but it's good to check.

If we're doing this, it might be good to also add some sort of build-time check to enforce using `libc_errno` only within `ErrnoCheckingTest` tests. Maybe a clang-tidy pass? Though we'd need to finish getting the other clang-tidy passes fixed as well.

https://github.com/llvm/llvm-project/pull/131650