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

[Joseph Huber via cfe-commits]

jhuber6 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`. 

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