[clang] [Clang] Allow simpler visibility annotations when targeting win32 and mingw (PR #133699)

[Nikolas Klauser via cfe-commits]

================
@@ -870,7 +873,8 @@ def NSReturnsMismatch : DiagGroup<"nsreturns-mismatch">;
 
 def IndependentClassAttribute : DiagGroup<"IndependentClass-attribute">;
 def UnknownAttributes : DiagGroup<"unknown-attributes">;
-def IgnoredAttributes : DiagGroup<"ignored-attributes">;
+def IgnoredAttributes : DiagGroup<"ignored-attributes",
+                                  [DllexportExplicitInstantiation]>;
----------------
philnik777 wrote:

I need some way to track that the attribute has been applied, even though it's being ignored. That's what the new attribute is for. This diagnostic is issued if the attribute has been ignored on the declaration and there is no attribute on the definition. Morally I'm still warning about the `__declspec(dllexport)`, even if it's internally a different attribute.

https://github.com/llvm/llvm-project/pull/133699