[macOS] Qt internal warning when FontMetrics is used

qt.qpa.fonts: Populating font family aliases took 75 ms. Replace uses of missing font family ".AppleSystemUIFont" with one that exists to avoid this cost. 

import QtQuick

Window {
    width: 640
    height: 480
    visible: true

    FontMetrics {
        id: fm
        font.italic: true // comment this to stop warning
        readonly property int textWidth: fm.advanceWidth('test')
    }
}