[compiler-rt] [libcxx] [libcxxabi] [libunwind] [libunwind][libcxx][libcxxabi][compiler-rt-builtins] Fix Exception Handling build for wasm (PR #79667)

[via cfe-commits]

================
@@ -12,6 +12,7 @@
 #ifndef __LIBUNWIND_EXT__
 #define __LIBUNWIND_EXT__
 
+#ifndef __wasm__
----------------
EricWF wrote:

I would much rather you guard the usage of this header in each file.

That way it's clear to the reader in context that the include is unused under a certain configuration.
If the entire file contains no WASM code, then it probably shouldn't mention WASM at all.

Can you please explain what the `__WASM_EXCEPTIONS__` or `__USING_WASM_EXCEPTIONS__` was? 


https://github.com/llvm/llvm-project/pull/79667