[clang] [libcxx] [libc++][Clang] Updated the diagnostics checks in libc++ tests. (PR #144220)

[Corentin Jabot via cfe-commits]

https://github.com/cor3ntin approved this pull request.

Can you update the title/description to reflect the entire change (ie reuse the title/description of the previous PR)? Otherwise LGTM

Thanks for fixing the libc++ tests

https://github.com/llvm/llvm-project/pull/144220