[llvm] [CI] Enable OpenMP and Offload runtime in premerge (PR #174955)

[Jan Patrick Lehr via llvm-commits]

jplehr wrote:

Current Windows error seems unrelated
```
++ sccache --zero-stats
sccache: error: Timed out waiting for server startup. Maybe the remote service is unreachable?
Run with SCCACHE_LOG=debug SCCACHE_NO_DAEMON=1 to get more information
```

https://github.com/llvm/llvm-project/pull/174955