title: Undefined symbols for architecture arm64 in Xcode 7.1
body: <p>Hi when I try to run my app in Xcode 7.1 on device , I am getting the following error. Can you pls let me know the issue. It runs fine on simulator.</p>
  
  <p>Undefined symbols for architecture arm64:
    "_OBJC_CLASS_$_ADAuthenticationContext", referenced from:
        objc-class-ref in LoadingViewController.o
  ld: symbol(s) not found for architecture arm64
  clang: error: linker command failed with exit code 1 (use -v to see invocation)</p>