[clang] [llvm] [RISCV] Support RISC-V Profiles in -march option (PR #76357)

[Philip Reames via cfe-commits]

https://github.com/preames commented:

After this was discussed at the sync-up call today, I believe we're in agreement on direction here.  This is close to being ready and is just pending some code cleanup.  

https://github.com/llvm/llvm-project/pull/76357