[llvm] [clang] [RISCV] Add -march support for many of the S extensions mentioned in the profile specification. (PR #79399)

[Wang Pengcheng via cfe-commits]

https://github.com/wangpc-pp commented:

[Ssstrict](https://github.com/riscv/riscv-profiles/commit/962bcc6764f3b6ccfbdcfe030c77b05c6a475c5e) too? I was going to add it but why not just hitchhike this PR? :-)

https://github.com/llvm/llvm-project/pull/79399