message: Check that qmake runs successfully and check Qt version
diff: @@ -8,6 +8,22 @@ endif()
  set(QMAKE_QT5_COMMAND ${QT_QMAKE_EXECUTABLE} CACHE STRING "Command to run to invoke Qt5's qmake. Normally this is qmake, possibly with qtchooser, but might be qmake-qt5")
  set(RENDERDOC_SWIG_PACKAGE https://github.com/baldurk/swig/archive/renderdoc-modified-7.zip CACHE STRING "The location where RenderDoc's swig fork source can be found. By default points to the URL on github but can be pointed to a local file.")
  +execute_process(
  + COMMAND ${QT_QMAKE_EXECUTABLE} -query QT_VERSION
  + WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}
  + OUTPUT_VARIABLE QT_VERSION
  + ERROR_VARIABLE QT_VERSION_STDERR
  + OUTPUT_STRIP_TRAILING_WHITESPACE
  + ERROR_STRIP_TRAILING_WHITESPACE
  + )
  +
  +# we need the trailing .999 since 5.5.1 would be VERSION_GREATER than 5.5 which implicitly means 5.5.0
  +if (QT_VERSION VERSION_GREATER 5.5.999)
  + message(STATUS "Building using Qt ${QT_VERSION}")
  +else()
  + message(FATAL_ERROR "${QT_QMAKE_EXECUTABLE} -query QT_VERSION returned: \"${QT_VERSION}\". Error output was: \"${QT_VERSION_STDERR}\". We require Qt >= 5.6 and for the qmake executable to run Qt5. Check your distribution for how to configure Qt5, you may need to set the QT_SELECT environment variable or customise the cmake variable QT_QMAKE_EXECUTABLE to qmake-qt5")
  +endif()
  +
  set(QMAKE_CONFIG "debug")
  set(QMAKE_LDFLAGS "")
  set(QMAKE_CXXFLAGS "")
  