[clang] [clang-tools-extra] [llvm] [LLVM][CLANG] Update signal-handling behavior to comply with POSIX (PR #169340)

[Xing Xue via llvm-commits]

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@@ -398,7 +398,11 @@ static void installExceptionOrSignalHandlers() {
   sigemptyset(&Handler.sa_mask);
 
   for (unsigned i = 0; i != NumSignals; ++i) {
-    sigaction(Signals[i], &Handler, &PrevActions[i]);
+    struct sigaction act;
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xingxue-ibm wrote:

Changed to guard the new behavior with `NeedsPOSIXUtilitySignalHandling`. Thanks!

https://github.com/llvm/llvm-project/pull/169340