[inductor] Make OpenMP work in fbcode (#105777)
Since we use libomp instead of libgomp, we need to suppress -fopenmp
at link time (using it only at preproc time), and explicitly link libomp.so.
Differential Revision: [D47692939](https://our.internmc.facebook.com/intern/diff/D47692939/)
**NOTE FOR REVIEWERS**: This PR has internal Meta-specific changes or comments, please review them on [Phabricator](https://our.internmc.facebook.com/intern/diff/D47692939/)!
Pull Request resolved: https://github.com/pytorch/pytorch/pull/105777
Approved by: https://github.com/jansel
