[qmltc] build error with QT_NO_URL_CAST_FROM_STRING

QtObject {
    readonly property FontLoader iconLoader: FontLoader {
        source: "qrc:/qt/qml/path/to/font.ttf"
    }

this->setSource((QString(QtPrivate::qMakeStringPrivate(u"" "qrc:/qt/qml/path/to/font.ttf"))));