[compiler-rt] [tsan] Fix nested signal handling (PR #138599)

[Dmitry Vyukov via llvm-commits]

dvyukov wrote:

Oh, sorry, this got off my radar.
@vitalybuka can you please merge this, or ask somebody to merge? I do it so rarely lately that forgot all procedures.

https://github.com/llvm/llvm-project/pull/138599