[Libomptarget] Make plugins depend explicitly on `intrinsics_gen`

Summary:
It's possible for the OpenMP offloading plugins to be build before
tablegen is run despite the fact that we rely on it. Simply make it
depend on it currently.
GitOrigin-RevId: 9f0321ccf118b37e5cb93cabd2acbf600c36b6ee
1 file changed