QmlDesigner: Do not require a qmake project for designer import paths

Let's enable all build system plugins to provide this information.

Task-number: QTCREATORBUG-20810
Change-Id: I0ef953e3c2c9a2be1fc4187e93232e9a2aeacafd
Reviewed-by: hjk <hjk@qt.io>
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>
Reviewed-by: Thomas Hartmann <thomas.hartmann@qt.io>

src/plugins/projectexplorer/target.cpp

@@ -673,6 +673,11 @@ void Target::setNamedSettings(const QString &name, const QVariant &value)
         d->m_pluginSettings.insert(name, value);
 }
 
+QVariant Target::additionalData(Core::Id id) const
+{
+    return project()->additionalData(id, this);
+}
+
 void Target::updateDeviceState()
 {
     IDevice::ConstPtr current = DeviceKitInformation::device(kit());