[llvm] [IR] Add llvm `clmul` intrinsic (PR #140301)

[Oscar Smith via llvm-commits]

oscardssmith wrote:

also the RiscV tests I've added are very much not working. Running `bin/llvm-lit -v llvm/test/CodeGen/RISCV/rv32zbc-zbkc-intrinsic.ll` gives 
```
Callsite was not defined with variable arguments!
ptr @llvm.clmul.i32
```
Any idea what this means?

https://github.com/llvm/llvm-project/pull/140301