OGS_BUILD_GUI=ON does not work with CMake >= 3.9
CMake 3.9.0 introduced some changes which fails CMake configuration because of a cyclic dependency between VtkVis and QtDataView targets even when building static libraries (was the case just for dynamic libs before).
Advice for now: stay on CMake 3.8.x!
- tested CMake 3.9.1: still there.