I know that Oatie brand glues make one specific for bonding PVC to ABS. I know that normal PVC glue will still work, you just might not get the max strength out of the fitting.
Being that skimmers/drains are suction side and see little pressure, unlikely to cause problem. Make sure you scuff both sides of the fittings with some sandpaper/emery cloth before gluing.
I used standard PVC glue on my drains/skimmers and pressure tested to 60 psi with no problems...
Just make sure you pressure test BEFORE shooting the gunite!
Also note...When you plug the 2" threaded ports in your drains/skimmers for the pressure test, PTFE paste works much better than teflon tape to seal them.