[compiler-rt] [sanitizer_common] Block asynchronous signals only (PR #98200)

[Thurston Dang via llvm-commits]

thurstond wrote:

> This patch broke the [Solaris/amd64 buildbot](https://lab.llvm.org/staging/#/builders/94/builds/5085). Solaris currently lacks `internal_sigdelset` (and some other non-Linux targets probably too).

Thanks for the report and sorry for the inconvenience! I've fixed-forward in https://github.com/llvm/llvm-project/commit/6789e1bb77c030c25ba5686c784bf4966770c324 to limit the change to Linux only.

https://github.com/llvm/llvm-project/pull/98200