linking against qt5 library

[mameyer]

rock_widget_collection links against qt4 and qt5. See the output of ldd below

ldd librock_widget_collection.so | grep 'Qt'
libQtGui.so.4 => /usr/lib/x86_64-linux-gnu/libQtGui.so.4
libQtCore.so.4 => /usr/lib/x86_64-linux-gnu/libQtCore.so.4
libQtOpenGL.so.4 => /usr/lib/x86_64-linux-gnu/libQtOpenGL.so.4
libQtDesigner.so.4 => /usr/lib/x86_64-linux-gnu/libQtDesigner.so.4
libosgQt.so.100 => /usr/lib/x86_64-linux-gnu/libosgQt.so.100
libQt5Test.so.5 => /usr/lib/x86_64-linux-gnu/libQt5Test.so.5
libQt5OpenGL.so.5 => /usr/lib/x86_64-linux-gnu/libQt5OpenGL.so.5
libQt5Widgets.so.5 => /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
libQt5Gui.so.5 => /usr/lib/x86_64-linux-gnu/libQt5Gui.so.5
libQt5Core.so.5 => /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
libQtScript.so.4 => /usr/lib/x86_64-linux-gnu/libQtScript.so.4
libQtXml.so.4 => /usr/lib/x86_64-linux-gnu/libQtXml.so.4
libQtSvg.so.4 => /usr/lib/x86_64-linux-gnu/libQtSvg.so.4

[doudou]

Just go the problem as well after I explicitely removed qwt from my system ... The CMake code was picking up the qt5 version and boom.

#22 should fix the problem. I haven't tested the case where QWT is present yet ...