Without QT, CMake fails:

```
CMake Error at /usr/share/cmake-2.8/Modules/FindPackageHandleStandardArgs.cmake:97 (MESSAGE):
  Could NOT find Qt4 (missing: QT_QMAKE_EXECUTABLE QT_MOC_EXECUTABLE
  QT_RCC_EXECUTABLE QT_INCLUDE_DIR QT_LIBRARY_DIR QT_QTCORE_INCLUDE_DIR
  QT_QTCORE_LIBRARY QT_QTGUI_INCLUDE_DIR QT_QTGUI_LIBRARY
  QT_QTTEST_INCLUDE_DIR QT_QTTEST_LIBRARY QT_UIC_EXECUTABLE)
Call Stack (most recent call first):
  /usr/share/cmake-2.8/Modules/FindPackageHandleStandardArgs.cmake:288 (_FPHSA_FAILURE_MESSAGE)
  /usr/share/cmake-2.8/Modules/FindQt4.cmake:1200 (FIND_PACKAGE_HANDLE_STANDARD_ARGS)
  examples/CalcQt/CMakeLists.txt:3 (find_package)


-- Configuring incomplete, errors occurred!
```

Can you make it optional? You can simply skip it if QT libs are not found or prompt a warning message and continue.