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

[via llvm-commits]

joshua-arch1 wrote:

> Add it to `../clang/lib/Frontend/CompilerInvocation.cpp:4228`
Can't we use "-fopenmp -fopenmp-targets=riscv64-unknown-linux-gnu"? It will show '-fopenmp-targets' must be used in conjunction with a '-fopenmp' option compatible with offloading; e.g., '-fopenmp=libomp' or '-fopenmp=libiomp5'.

For other target like powerpc, I can use "-fopenmp -fopenmp-targets=powerpc64le" without errors.

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