VTK 8.90 missing vtkGUISupportQt_LOADED

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@bill From what I can see there is no longer a VTK_QT_VERSION variable:

vtkGUISupportQt_LOADED: 
We have GUISupportQt
VTK_VERSION: 8.90.0
VTK_QT_VERSION: 
VTKWikiExamples: Building Qt examples
CMake Error at /usr/local/share/cmake-3.13/Modules/FindQt4.cmake:1313 (message):
  Found unsuitable Qt version "5.12.0" from
  /home/amaclean/Qt/5.12.0/gcc_64/bin/qmake, this code requires Qt 4.x
Call Stack (most recent call first):
  CMakeLists.txt:150 (find_package)

I also built VTK with VTK_GROUP_ENABLE_QT:WANT and VTK_GROUP_ENABLE_QT:YES, VTK_QT_VERSION remains empty.

In looking at VTK/Examples/GUI/Qt only Qt 5.x seems to be supported.