title: Build Failure for iOS on Unity/Xcode
body: <p>I'm currently trying to set up a Unity project that's set up for VR into AR for iOS. I'm using the AR Foundation plugin + ARKit/ARCore plugins. Trying to build it and run on my iPhone using Xcode and I'm getting these errors.</p>
  
  <p>Tried changing a bunch of player settings.</p>
  
  <pre><code>Undefined symbols for architecture arm64:
    "_OBJC_CLASS_$_AREnvironmentProbeAnchor", referenced from:
        objc-class-ref in UnityARKit.a(ARKitXREnvironmentProbeProvider.o)
    "_OBJC_CLASS_$_ARCollaborationData", referenced from:
        objc-class-ref in UnityARKit.a(ARKitXRSessionProvider.o)
    "___isPlatformVersionAtLeast", referenced from:
        _UnityARKit_Camera_AcquireConfigurations in UnityARKit.a(ARKitXRCameraProvider.o)
        _UnityARKit_Camera_TryGetCurrentConfiguration in UnityARKit.a(ARKitXRCameraProvider.o)
        _UnityARKit_Camera_TrySetCurrentConfiguration in UnityARKit.a(ARKitXRCameraProvider.o)
        (anonymous namespace)::ARKitXRCameraProvider::ResetLocalConfigurationState() in UnityARKit.a(ARKitXRCameraProvider.o)
        (anonymous namespace)::ARKitXRCameraProvider::HandleARKitEvent(UnityARKitEvent, void*, int) in UnityARKit.a(ARKitXRCameraProvider.o)
        _UnityARKit_EnvironmentProbeProvider_Construct in UnityARKit.a(ARKitXREnvironmentProbeWrapper.o)
        _UnityARKit_EnvironmentProbeProvider_Destruct in UnityARKit.a(ARKitXREnvironmentProbeWrapper.o)
        ...
    "_OBJC_CLASS_$_ARBodyAnchor", referenced from:
        objc-class-ref in UnityARKit.a(ARKitXRHumanBodyProvider.o)
    "_OBJC_CLASS_$_ARImageTrackingConfiguration", referenced from:
        objc-class-ref in UnityARKit.a(ARKitXRImageTrackingProvider.o)
    "_OBJC_CLASS_$_ARBodyTrackingConfiguration", referenced from:
        objc-class-ref in UnityARKit.a(ARKitXRHumanBodyProvider.o)
    "_OBJC_CLASS_$_ARImageAnchor", referenced from:
        objc-class-ref in UnityARKit.a(ARKitXRImageTrackingProvider.o)
    "_OBJC_CLASS_$_ARSkeletonDefinition", referenced from:
        objc-class-ref in UnityARKit.a(ARKitXRHumanBodyProvider.o)
    "_OBJC_CLASS_$_ARObjectAnchor", referenced from:
        objc-class-ref in UnityARKit.a(ARKitXRObjectTrackingProvider.o)
    "_OBJC_CLASS_$_ARReferenceImage", referenced from:
        objc-class-ref in UnityARKit.a(ARKitXRImageTrackingProvider.o)
    "_OBJC_CLASS_$_ARMatteGenerator", referenced from:
        objc-class-ref in UnityARKit.a(ARKitXRHumanBodyProvider.o)
    "_OBJC_CLASS_$_ARReferenceObject", referenced from:
        objc-class-ref in UnityARKit.a(ARKitXRObjectTrackingProvider.o)
  ld: symbol(s) not found for architecture arm64
  clang: error: linker command failed with exit code 1 (use -v to see invocation)
  </code></pre>