As far as I can tell p4vc as shipped with p4v just straight up doesn't work in Linux. I'm using version 2015.2.1315639 of P4V, which I believe is the latest version for Linux x64. It needs a wrapper to get LD_LIBRARY_PATH, etc set up properly, the same as p4v and other Qt-based tools. The wrapper script that's used with p4v, p4merge, and p4admin can also be used to wrap p4vc. I suggest you rename the p4vc binary to p4vc.bin and make a new copy of your wrapper script called p4vc that will call it.
I'm the maintainer of the p4v install script for Slackware and that's exactly what our install script does. See https://slackbuilds.org/slackbuilds/14.2/development/p4v/p4v.SlackBuild.
The benefit of implementing this idea is that p4vc will work.