[clang] [llvm] [RISCV][FMV] Support target_clones (PR #85786)

[Piyou Chen via llvm-commits]

BeMg wrote:

1. Suppress the warning `warn_target_clone_mixed_values` for RISC-V
2. Update `__riscv_ifunc_select`. From `__riscv_ifunc_select(char *)` into `__riscv_ifunc_select(unsigned long long, unsigned long long )`. 
3. Add one more error messenge when there are +extension that hwprobe can't detect.

https://github.com/llvm/llvm-project/pull/85786