[clang] [llvm] [RISCV] Support __builtin_cpu_init and __builtin_cpu_supports (PR #99700)

[Philip Reames via llvm-commits]

preames wrote:

I've gone ahead and merged this into main.  We have missed the branch creation, so without further action this will not be included in 19.x.  We need to ensure the constructor change for compiler-rt lands, and then backport them together if we choose to.  

https://github.com/llvm/llvm-project/pull/99700