[compiler-rt] [sanitizer_common] AND signals in BlockSignals instead of deleting (PR #113443)

[Thurston Dang via llvm-commits]

thurstond wrote:

> It would be nice to test, but I guess it's hard with lit-test. Maybe in common unit test.

I've added a test, please review.

https://github.com/llvm/llvm-project/pull/113443