[libunwind] [libunwind] Tweak tests for musl support. (PR #85097)

[Louis Dionne via cfe-commits]

================
@@ -24,16 +23,30 @@
 #include <unistd.h>
 #include <unwind.h>
 
+// Note: this test fails on musl because:
+//
+//  (a) musl disables emission of unwind information for its build, and
+//  (b) musl's signal trampolines don't include unwind information
+//
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ldionne wrote:

This comment is not generally useful. Let's remove it.

I could see this comment on an annotation like `// XFAIL: <arch>-<vendor>-musl` or something like that, but we don't seem to have that. Or if that's the purpose of changing the `REQUIRES` to `linux-gnu` above, then this should be explained in close proximity with that `REQUIRES:` annotation.

https://github.com/llvm/llvm-project/pull/85097