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

[Thomas Fransham via cfe-commits]

fsfod wrote:

@john-brawn-arm This may be hard to remember, but this a path you've tread before could the LLVM_INSTANTIATE_REGISTRY just be changed to a fulll class explicit template instantiation?


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