[clang] [Clang] Enable multilib library support for Linux/Windows (PR #188584)

[Michael Platings via cfe-commits]

mplatings wrote:

I no longer work in this area but I can offer a historical perspective. multilib.yaml was originally developed with BareMetal as the primary use case, but it was always intended that other toolchains could benefit from it as well, should the necessary plumbing be put in place. This change looks like a positive step in that direction.
I've looked over the BareMetal refactoring and that LGTM. I don’t have sufficient familiarity with the other toolchains to comment there, so it would be good to have people with experience in those areas take a look, in particular with respect to how it might interact with existing multilib systems.
Overall I am +1 on this change.

https://github.com/llvm/llvm-project/pull/188584