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

[Andrew Ng via cfe-commits]

nga888 wrote:

> > I did briefly think about this, but does this change really apply to `GetOrCreateLLVMGlobal`? Is there any test case to exercise it? Perhaps it would be better to leave `GetOrCreateLLVMGlobal` as is?
> 
> I think we should look at it the other way around: unless there's a reason that the functions should behave differently (and I'm not aware of any), it seems better for them to keep using the same logic.

One function handles "functions" and the other "globals", so behaviour is not necessarily the same. However, if you feel it would be better that both use the same logic, then I will go ahead with adding this.

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