[llvm] [Offload] Add support for riscv64 to host plugin (PR #115773)

[via llvm-commits]

joshua-arch1 wrote:

> `libomp` doesn't support RISC-V yet. There is a PR but the author doesn't know whether it works properly or not.

To be exact, I think it is libomptarget that does not support RISC-V yet. Since the target offloading openmp runtime libaray cannot work on RISC-V, I suppose the host plugin patch cannot work normally.

https://github.com/llvm/llvm-project/pull/115773