[clang] [CIR] Unblock simple C++ structure support (PR #138368)

[Morris Hafner via cfe-commits]

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@@ -12,6 +12,17 @@ IncompleteS *p;
 // LLVM: @p = dso_local global ptr null
 // OGCG: @p = global ptr null, align 8
 
+struct CompleteS {
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mmha wrote:

Do simple union work with this? If so, can you add a test for those, too?

https://github.com/llvm/llvm-project/pull/138368