[clang] [llvm] [LLVM][Support] Enforce proper instantiations of `Registry<T>` (PR #185141)

[Tomohiro Kashiwada via llvm-commits]

kikairoya wrote:

> I would prefer that we had similar behavior across platforms (`__declspec(dllexport)` on windows, `__attribute __((__visibility __("default")))` on other platforms)

I agree, but I'd leave it for now since I'm preparing PRs to replace the uses of the old macro and deprecate it.

https://github.com/llvm/llvm-project/pull/185141