Qnx: Use QFile instead of QTemporary to create the project's bar-descriptor

This enables developers to find and use the prepared bar-descriptor with command lines

Change-Id: I1083d18f02d5026e186735fdfcbb61aca30f01b8
Reviewed-by: Tobias Nätterlund <tobias.naetterlund@kdab.com>
Reviewed-by: Nicolas Arnaud-Cormos <nicolas@kdab.com>

src/plugins/qnx/blackberryabstractdeploystep.cpp

@@ -98,7 +98,6 @@ void BlackBerryAbstractDeployStep::run(QFutureInterface<bool> &fi)
 
     // Finished
     m_params.clear();
-    cleanup();
     m_processCounter = -1;
 
     m_timer->stop();