message: respect qtViewer build option in CMake
diff: @@ -65,8 +65,10 @@ ENDIF()
  # qt-based viewer for geometry (and soon volumes)
  IF(NOT (APPLE AND OSPRAY_COMPILER_ICC) AND NOT WIN32)
  OPTION(OSPRAY_APPS_QTVIEWER "Build ospQtViewer (Qt-based model viewer)" ON)
  + IF(OSPRAY_APPS_QTVIEWER)
  ADD_SUBDIRECTORY(qtViewer)
  ENDIF()
  +ENDIF()
  # volume viewer application
  IF(NOT (APPLE AND OSPRAY_COMPILER_ICC))
  