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

[Erich Keane via cfe-commits]

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@@ -998,6 +998,9 @@ def warn_npot_ms_struct : Warning<
   "data types with sizes that aren't a power of two">,
   DefaultError, InGroup<IncompatibleMSStruct>;
 
+def err_itanium_layout_unimplemented : Error<
+  "sorry, Itanium-compatible layout is unimplemented for the current C++ ABI">;
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erichkeane wrote:

this isn't really a good error format, please try to make this look more like our other diagnostics.

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