[clang] [clang-tools-extra] [flang] [llvm] Reland 'Update llvm::Registry to work for LLVM shared library builds on windows' (#109024) (PR #112640)

[Nico Weber via cfe-commits]

nico wrote:

This seems to break building of clang-tools-extra binaries: http://45.33.8.238/win/95986/step_3.txt

Please take a look and revert for now if it takes a while to fix.

https://github.com/llvm/llvm-project/pull/112640