[clang] [Clang][RISCV] Support -fcf-protection=return for RISC-V (PR #112477)

[Jesse Huang via cfe-commits]

jaidTw wrote:

After a meeting with Kito, I will change the requirement of both patches (this and 112478) to Zicfiss, and lift it in a future patch
I'm encountering a problem that cc1 tests cannot recognize the option and working of a fix now

https://github.com/llvm/llvm-project/pull/112477