Utkarsh Ayachit authored Aug 02, 2016 and Ben Boeckel committed Mar 07, 2017

Similar to what we're doing with Qt5, this change now adds called to
vtk_module_export_code_find_package() for Qt4. That way, when importing
a module using Qt4, we automatically find Qt4.

Also changed to use imported targets rather than library paths when
linking to Qt4 libraries.