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

[via cfe-commits]

================
@@ -36,7 +36,12 @@ struct __cxa_exception;
 _LIBCPP_OVERRIDABLE_FUNC_VIS __cxa_exception* __cxa_init_primary_exception(
     void*,
     std::type_info*,
-    void(
+#  if defined(__USING_WASM_EXCEPTIONS__)
----------------
trcrsired wrote:

yeah. but here's a problem. __USING_WASM_EXCEPTIONS__ is not defined by clang 19 even with -fwasm-exceptions enabled. i suggest to just use __wasi__ macro, instead of __USING_WASM_EXCEPTIONS__ 

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