QmlDesigner.Instances: fix for Mac OS and Qt 4

The QSharedMemory implementations of Qt5 and Qt4
on Mac seem to be incompatible.

We seem to have the same bug casually for Linux.

Until we solve the real issue this serves as a quick fix.

Change-Id: I686e3e94b6bb777b96f8c68cac6036c18b8d070d
Reviewed-by: Marco Bubke <marco.bubke@digia.com>

src/plugins/qmldesigner/designercore/instances/nodeinstanceserverproxy.cpp

@@ -158,6 +158,10 @@ NodeInstanceServerProxy::NodeInstanceServerProxy(NodeInstanceView *nodeInstanceV
 
    QProcessEnvironment enviroment = QProcessEnvironment::systemEnvironment();
 
+#if (QT_VERSION < QT_VERSION_CHECK(5, 0, 0)) && (defined(Q_OS_MAC) || defined(Q_OS_LINUX))
+   enviroment.insert(QLatin1String("DESIGNER_DONT_USE_SHARED_MEMORY"), QLatin1String("1"));
+#endif
+
    if (QFileInfo(applicationPath).exists()) {
        m_qmlPuppetEditorProcess = new QProcess;
        m_qmlPuppetEditorProcess->setProcessEnvironment(enviroment);