[libcxx-commits] [libcxx] Update testing documentation with testing guidelines. (PR #87928)

[Christopher Di Bella via libcxx-commits]

https://github.com/cjdb requested changes to this pull request.

Overall, this looks great, thanks for writing it up! Got some suggestions, and I think we can work through those to have a top-tier document.

https://github.com/llvm/llvm-project/pull/87928