[clang] [RISCV] Add -march string as Module metadata in IR. (PR #80760)

[Paul Kirth via cfe-commits]

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

Thank you for this. I expect this to be a big help w/ the various target features bugs we've seen in LTO builds.

I'm surprised only 1 test file needed the metadata updated as a result of this change.

https://github.com/llvm/llvm-project/pull/80760