[llvm] [CI][flang][OpenMP] Build OpenMP runtime mod files for flang tests (PR #206517)

[Jan André Reuter via llvm-commits]

Thyre wrote:

> Note on CI failures: these seem to be failures in offload/ unrelated to my patch.

They should be resolved in the next CI run, as the PR that caused these build failures was reverted (see https://github.com/llvm/llvm-project/pull/206523)

https://github.com/llvm/llvm-project/pull/206517