[clang] [llvm] Update llvm::Registry to work for LLVM shared library builds on windows (PR #109024)

[Saleem Abdulrasool via cfe-commits]

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@@ -189,19 +190,23 @@
 #define LLVM_TEMPLATE_ABI __declspec(dllimport)
 #define LLVM_EXPORT_TEMPLATE
 #endif
+#define LLVM_ABI_EXPORT __declspec(dllexport)
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compnerd wrote:

Why is this being added? I'm weary of any macro that is always export only because the value needs to switch between the definition and reference.

https://github.com/llvm/llvm-project/pull/109024