[llvm] [offload] Standalone build fixes (PR #118173)

[Michał Górny via llvm-commits]

mgorny wrote:

Ok, I think it's ready. The remaining test failures I see are in `amdgcn-amd-amdhsa` tests, and they fail with regular build for me as well. I'm guessing it's because I don't have HSA installed.

https://github.com/llvm/llvm-project/pull/118173