[clang] [driver] mark offload.f90 as REQUIRES: openmp_runtime (PR #181759)

[Henrik G. Olsson via cfe-commits]

hnrklssn wrote:

> > In our downstream repo the test case fails with `error: unsupported option '-fopenmp'`. This was the only REQUIRES feature related to OpenMP I could find, but if it's not appropriate for this test case I can manually disable the test downstream instead.
> 
> That's bizarre, I haven't seen any bots complain about this so I am unsure if it's a problem that only exists in your fork. Using `-fopenmp` in this manner should only add certain arguments to the generated commands, but I am not overly familiar with the details of `flang`.

AppleClang does not support OpenMP at all at this point, and there doesn't seem to exist a catch-all `REQUIRES: openmp` to tag tests with. Closing this in favour of a downstream fix.

https://github.com/llvm/llvm-project/pull/181759