[clang] [clang] Fix loss of `dllexport` for exported template specialization (PR #94664)

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https://github.com/zmodem commented:

Thanks! This basically looks good to me.

It would be nice to keep `GetOrCreateLLVMGlobal` and `GetOrCreateLLVMFunction` in sync. Would it be possible to extract the "Handle dropped DLL attributes" logic into a small utility function that could be called from both?

https://github.com/llvm/llvm-project/pull/94664