[clang] [Clang] [Driver] use __cxa_atexit by default on Cygwin. (PR #135701)

[Martin Storsjö via cfe-commits]

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@@ -7230,7 +7230,9 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   // -fuse-cxa-atexit is default.
   if (!Args.hasFlag(
           options::OPT_fuse_cxa_atexit, options::OPT_fno_use_cxa_atexit,
-          !RawTriple.isOSAIX() && !RawTriple.isOSWindows() &&
+          !RawTriple.isOSAIX() &&
+              (!RawTriple.isOSWindows() ||
+               RawTriple.isWindowsCygwinEnvironment()) &&
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mstorsjo wrote:

As GCC doesn't use `__cxa_atexit` on mingw, we probably shouldn't change it unless we have good reason to do it. Best case it would be a simple uneventful change, worst case it would lead to a can of worms of breaking subtle things somewhere...

https://github.com/llvm/llvm-project/pull/135701