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

[Erich Keane via cfe-commits]

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@@ -302,6 +302,11 @@ Attribute Changes in Clang
   to reduce the size of the destroy functions for coroutines which are known to
   be destroyed after having reached the final suspend point.
 
+- On targets with C++ ABI other than Microsoft, Clang now supports
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erichkeane wrote:

This should just say 'Itanium' rather than talking around it (other than Microsoft).

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