title: Xcode 9 GM undefined symbols for architecture arm64
body: <p>In Xcode 9's GM release, I am getting some compile-time errors for <code>undefined symbols for architecture arm64</code>, namely for AVFoundation with:</p>
  
  <ul>
  <li><code>AVCapturePhotoOutput().supportedFlashModes</code></li>
  <li><code>AVCapturePhotoSettings().availablePreviewPhotoPixelFormatTypes</code></li>
  </ul>
  
  <p>In both cases, using their "undocumented" <code>__supportedFlashModes</code>/<code>__availablePreviewPhotoPixelFormatTypes</code> builds just fine.</p>
  
  <ol>
  <li>Has anybody encountered the same issues in other frameworks?</li>
  <li><a href="https://developer.apple.com/documentation/avfoundation/avcapturephotosettings?changes=latest_minor" rel="noreferrer">API does not document such breaking changes</a>, is this a bug?</li>
  </ol>