[clang] [flang] [llvm] [clang] Add isOffloadingTarget function to LangOpts (PR #126956)

[Joseph Huber via llvm-commits]

https://github.com/jhuber6 approved this pull request.

Seems reasonable so long as we know that `SPIR-V` is always a GPU. I'll defer to SPIR people.

https://github.com/llvm/llvm-project/pull/126956