title: ARKit: how to correctly check for supported devices?
body: <p>I'm using <code>ARKit</code> but it is not a core functionality in my app, so I'm not setting the <code>arkit</code> key in the <code>UIRequiredDeviceCapabilities</code>. I'm setting the directive <code>@available(iOS 11.0, *)</code>, but <code>ARKit</code> requires an <strong>A9</strong> processor or above (that is, <strong>iPhone 6S</strong> or newer...)</p>
  
  <p>What the best way to check that? I've found a workaround that involves <a href="https://stackoverflow.com/questions/26028918/how-to-determine-the-current-iphone-device-model">checking the device model</a> in several places, but it looks like it's a bit complicated. And would this be rejected in a review for the Store?</p>