Qt should use `OpenGL_GL_LIBRARY` as a hint for `Qt5Gui_GL_LIBRARY`

When using `Qt5Gui` via CMake, it searches for `libGL` on its own. It would be great if when finding `Qt5Gui_EGL_LIBRARY`, it would use the `FindOpenGL` variables for the libraries if they're available. This ensures that all GL-using libraries are using the same `libGL` and `libEGL` and avoids warnings about conflicting paths for libraries such as:

CMake Warning at CMake/vtkModule.cmake:2857 (add_library):
Cannot generate a safe runtime search path for target GUISupportQt because
files in some directories may conflict with libraries in implicit
directories:

runtime library [libGL.so.1] in /usr/lib/x86_64-linux-gnu may be hidden by files in:
/usr/lib/nvidia-410

Some of these libraries may not be found correctly.
Call Stack (most recent call first):
GUISupport/Qt/CMakeLists.txt:57 (vtk_module_add_module)