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

[Thomas Fransham via cfe-commits]

fsfod wrote:

Its strange that visibility macros are enabled for windows but its not a shared library build, idk if the gn build script need to be manually updated to define the macros correctly to turn off visibility macros by default.

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