If the squeak doesn't change significantly when the AC compressor clutch engages, then its probably not the compressor. Engaged vs disengaged is a different set of bearings and also rules out the clutch itself. So that would be a good test for peace of mind.
Expect the frequency of the squeak to change though because engaging the AC clutch will cause a fluctuation in engine RPM and load on the belt.
Let us know how it sounds.