QmlProject: Avoid error messages about missing build configurations

Override the target setup, so that we don't try to initialize build
configurations.

Change-Id: I8f8022c705ea54dd66df828fdb4837d4a41bc96e
Reviewed-by: hjk <hjk@qt.io>

src/plugins/qmlprojectmanager/qmlproject.h

@@ -72,6 +72,7 @@ public:
 
 protected:
     RestoreResult fromMap(const QVariantMap &map, QString *errorMessage) override;
+    bool setupTarget(ProjectExplorer::Target *t) override;
 
 private:
     void generateProjectTree();