[clang] [clang] Stub out gcc_struct attribute (PR #71148)

[Fangrui Song via cfe-commits]

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@@ -3618,6 +3618,13 @@ void CompilerInvocationBase::GenerateLangArgs(const LangOptions &Opts,
     GenerateArg(Consumer, OPT_fcxx_abi_EQ,
                 TargetCXXABI::getSpelling(*Opts.CXXABI));
 
+  if (Opts.MSBitfields.has_value()) {
+    if (Opts.MSBitfields.value())
+      GenerateArg(Consumer, OPT_mms_bitfields);
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MaskRay wrote:

If we use `BoolOption` in `Options.td`, we won't need this custom code.

https://github.com/llvm/llvm-project/pull/71148