[llvm] [LLVM-C] Upstream `LLVMBuild{Min, Max}Num` from rustc (PR #162500)

[Nikita Popov via llvm-commits]

https://github.com/nikic commented:

I'm not sure why we have these functions on the Rust side at all. minnum and maxnum are just normal intrinsics, so we should just do something like `self.call_intrinsic("llvm.minnum", &[self.val_ty(lhs)], &[lhs, rhs])`.

https://github.com/llvm/llvm-project/pull/162500