ProjectWindow: Delay panel update after target adding

Parts of the machinery are not yet done when the signal
arrives, waiting for next event loop iteration suffices
to get a context enabling us to show the proper panel.

Change-Id: Icbf33a4f5a900058ecc89ac125eb43313e12b74f
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/projectexplorer/targetsettingspanel.cpp

@@ -701,7 +701,7 @@ TargetGroupItem::TargetGroupItem(const QString &displayName, Project *project)
     QObject::connect(project, &Project::removedTarget,
             d, &TargetGroupItemPrivate::handleTargetRemoved);
     QObject::connect(project, &Project::activeTargetChanged,
-            d, &TargetGroupItemPrivate::handleTargetChanged);
+            d, &TargetGroupItemPrivate::handleTargetChanged, Qt::QueuedConnection);
 }
 
 TargetGroupItem::~TargetGroupItem()