[clang] [llvm] Add clang driver changes to support MTI RISC-V (PR #134065)

[Paul Kirth via cfe-commits]

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

LGTM. Probably give @mshockwave a chance to weigh in before landing, though.

https://github.com/llvm/llvm-project/pull/134065