Added debugging mode for simultaneous QML and C++ debugging

It's not yet possible to attach to an external app running a qml
debugging server, because the server is only started on startup if an
env variable is set. Changing this requires action from Brisbane, but
even the current solution works for C++ apps with QML in them.

Task-number: BAUHAUS-585
Reviewed-by: dt

src/plugins/qmlprojectmanager/qmlprojectconstants.h

@@ -54,6 +54,9 @@ const char * const QML_WIZARD_CATEGORY = "F.Projects"; // (after Qt)
 const char * const QML_WIZARD_TR_SCOPE = "QmlProjectManager";
 const char * const QML_WIZARD_TR_CATEGORY = QT_TRANSLATE_NOOP("QmlProjectManager", "Qt Quick Project");
 
+// Env variables for inspector
+const char * const E_QML_DEBUG_SERVER_PORT = "QML_DEBUG_SERVER_PORT";
+
 } // namespace Constants
 } // namespace QmlProjectManager