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

[Thomas Fransham via cfe-commits]

fsfod wrote:

It looks like that build bot has there own custom warning a errors set, but if i put the template static variable definitions back in the header Linux will have linker errors.

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