[llvm] [z/OS] Add backtrace support for z/OS. (PR #121826)

[Matt Arsenault via llvm-commits]

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@@ -708,13 +712,87 @@ static int unwindBacktrace(void **StackTrace, int MaxEntries) {
 }
 #endif
 
+#if ENABLE_BACKTRACES && defined(__MVS__)
+void zosbacktrace(raw_ostream &OS) {
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arsenm wrote:

```suggestion
static void zosbacktrace(raw_ostream &OS) {
```

https://github.com/llvm/llvm-project/pull/121826