Have you checked the QGroundControl Dev Guide, regarding pre-requisites and setting the environment for building the sources, especially regarding installing Qt?
As a side note, please be aware that the Qt version that Qt Creator is based on (in your example Qt Creator 5.0.2 based on Qt 5.12.2) is the version that somebody used to build the Qt Creator release you’re using, and may have not any relationship with the actual Qt version you have actually installed in your PC