[clang] [llvm] [RISCV] Avoid fatal error for SiFive CLIC preemptible frame pointers (PR #217949)

[Sam Elliott via cfe-commits]

https://github.com/lenary commented:

I think the wording needs to not mention `-fomit-frame-pointer`, because there are other reasons a frame pointer could be needed.

https://github.com/llvm/llvm-project/pull/217949