Support for Hopper (H100, GH200) GPUs

[smartalecH]

In order to support Hopper (H100) GPUs, then the Julia toolchain needs to also support LLVM v16. Currently, the latest pre-release (1.9) is building with LLVM v14.

One could always build Julia themselves using LLVM v16 (although this is considered "experimental"). It would be nice to raise this issue with the larger Julia dev community sooner than later, so that this step isn't needed.