I have added message("I am executed") in qwt.prf, executing qmake and watching the result on the compile output. I have this :

Qt Code: 
  1. 16:14:47: Running steps for project qwt_test...
  2. 16:14:47: Starting: "/home/developpeur/Qt5.0.2/5.0.2/gcc_64/bin/qmake" /home/developpeur/developpement/stageCamille/qwt_test/qwt_test.pro -r -spec linux-g++-64 CONFIG+=debug CONFIG+=declarative_debug CONFIG+=qml_debug
  3. 16:14:47: The process "/home/developpeur/Qt5.0.2/5.0.2/gcc_64/bin/qmake" exited normally.
  4. 16:14:47: Elapsed time: 00:00.
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Is it normal that "CONFIG+=qwt" is not written there ? It is actually in the .pro.
There is no mention of the message so I guess qwt.prf is not found.