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

[Aaron Ballman via cfe-commits]

https://github.com/AaronBallman commented:

Thank you for working on this, I'm super excited for the ability to write plugins that work on Windows!

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