[compiler-rt] [sanitizer-common] [Darwin] Provide warnings for common sandbox issues (PR #165907)

[Dan Blackwell via llvm-commits]

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

Thanks for this, looks good. Possibly could have been better to split across 2 separate PRs.

https://github.com/llvm/llvm-project/pull/165907