[clang] [WebAssembly] Define __USING_WASM_EXCEPTIONS__ for -fwasm-exceptions (PR #92604)

[Sam Clegg via cfe-commits]

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@@ -1006,6 +1006,8 @@ static void InitializePredefinedMacros(const TargetInfo &TI,
   else if (LangOpts.hasDWARFExceptions() &&
            (TI.getTriple().isThumb() || TI.getTriple().isARM()))
     Builder.defineMacro("__ARM_DWARF_EH__");
+  else if (LangOpts.hasWasmExceptions() && TI.getTriple().isWasm())
+    Builder.defineMacro("__USING_WASM_EXCEPTIONS__");
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sbc100 wrote:

How about just calling this `__WASM_EXCEPTIONS__`?

https://github.com/llvm/llvm-project/pull/92604