[libunwind] [libunwind] Add initial ARM64EC support (PR #138583)

[Jacek Caban via cfe-commits]

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@@ -1181,7 +1228,9 @@ DEFINE_LIBUNWIND_FUNCTION(__unw_getcontext)
 
 #endif
 
+#ifndef __arm64ec__
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cjacek wrote:

That's because the alias is more complex, it needs to account for mangled symbol names and requires an additional unmangled weak anti-dependency. Ideally, exports would use the demangled form, although the mangled version would likely still work. I moved the EC alias definition here to keep things cleaner.

https://github.com/llvm/llvm-project/pull/138583