[Travis] Set the qmake path again.

CMake/ctkTravisDashboardScript.cmake

@@ -18,6 +18,10 @@ if(NOT CTK_QT_VERSION)
   set(CTK_QT_VERSION 4)
 endif()
 
+if(CTK_QT_VERSION EQUAL 4)
+  set(QT_QMAKE_EXECUTABLE "/usr/bin/qmake")
+endif()
+
 #
 # Dashboard properties
 #