[clang] [Clang][Driver] Add option to provide path for multilib's YAML config file (PR #109640)

[via cfe-commits]

https://github.com/ArcaneNibble approved this pull request.

I am okay with this code as it relates to the RISC-V-related logic that I most recently touched.

All of this code related to munging multilib paths and sysroots is now rather difficult to follow with how many different pieces of code are involved, and I think that someone should refactor it at some point.



https://github.com/llvm/llvm-project/pull/109640