[llvm] [clang] [RISCV] Implement shadow stack on shadow stack mode with Zicfiss. (PR #68075)

[Paul Kirth via cfe-commits]

https://github.com/ilovepi commented:

Should the driver issue an error when using `-mforced-sw-shadow-stack` w/o `Zicfiss`? As mentioned in-line, I'm not sure we can do that check, but it feels like it should be incompatible.

https://github.com/llvm/llvm-project/pull/68075