There's no way to easily predict supplement interactions. Having said that, hypothetically, the Phenibut could perhaps decrease the effectiveness of Spike or may have no effect at all. It's difficult to say as you're talking about two main constituents where the mechanism(s) of action have yet to be fully elucidated.
I personally wouldn't recommend combining the two, but again, there's nothing definitive to support my opinion other than the fact that I'm never comfortable with combining multiple compounds which are neurologically active. The fewer, the better.