ENH: if qt4 qmake is found then set QT_QMAKE_EXECUTABLE to that value so that the same one will be used in FindQt4.cmake

Modules/FindQt.cmake

@@ -48,6 +48,7 @@ IF(QT_QMAKE_EXECUTABLE_FINDQT)
   EXEC_PROGRAM(${QT_QMAKE_EXECUTABLE_FINDQT} ARGS "-query QT_VERSION"
     OUTPUT_VARIABLE QTVERSION)
   IF(QTVERSION MATCHES "4.*")
+    SET(QT_QMAKE_EXECUTABLE ${QT_QMAKE_EXECUTABLE_FINDQT} CACHE PATH "QT4 qmake program.")
     SET(QT4_INSTALLED TRUE)
   ENDIF(QTVERSION MATCHES "4.*")
   IF(QTVERSION MATCHES "Unknown")