"AND signals in BlockSignals instead of deleting" doesn't work with Android

[thurstond]

The story so far:

• [sanitizer_common] Block asynchronous signals only llvm/llvm-project#98200 fixed a bug but caused a new bug.
• [sanitizer_common] AND signals in BlockSignals instead of deleting llvm/llvm-project#113443 largely fixes the issue from 98200 but broke the Android buildbot (https://lab.llvm.org/buildbot/#/builders/186/builds/3642).
  • Buildbot logs attached for posterity: Android-problems-yo.txt.
• Since Android's toolchain had never seen 98200, Reapply "[sanitizer_common] AND signals in BlockSignals instead of deleting (#113443)" for non-Android Linux only llvm/llvm-project#115790 reverts Android to the pre-98200 behavior. However, this means that Sanitizers unblock user blocked signals llvm/llvm-project#113385 is still not fixed for Android.