[compiler-rt] [sanitizer] Add cloak_sanitizer_signal_handlers runtime option (PR #162746)

[Thurston Dang via llvm-commits]

================
@@ -24,6 +24,9 @@ namespace __sanitizer {
 
 const char *SanitizerToolName = "SanitizerTool";
 
+const int MaxSignals = 64;
+bool signal_handler_is_from_sanitizer[MaxSignals] = {0};
----------------
thurstond wrote:

I will add atomicity.

I don't think it's feasible to combine SetSignalHandlerFromSanitizer/IsSignalHandlerFromSanitizer, because of this code in the sigaction interceptor:
```
  if (IsSignalHandlerFromSanitizer(signum) && ret == 0) {
    if (act)
      // If the user sets a signal handler, it is never cloaked, even if they
      // reuse a sanitizer's signal handler.
      SetSignalHandlerFromSanitizer(signum, false);

    ...
  }
```


https://github.com/llvm/llvm-project/pull/162746