title: Undefined symbols for architecture when add adMob
body: <p>I'm adding admob to my project, but I get this error: </p>
  
  <p>Undefined symbols for architecture i386:</p>
  
  <pre><code> "_OBJC_CLASS_$_EKEvent", referenced from:
        objc-class-ref in libGoogleAdMobAds.a(GADOpener.o)
    "_OBJC_CLASS_$_EKEventEditViewController", referenced from:
        objc-class-ref in libGoogleAdMobAds.a(GADOpener.o)
  ld: symbol(s) not found for architecture i386
  clang: error: linker command failed with exit code 1 (use -v to see invocation)
  </code></pre>
  
  <p>I have added:</p>
  
  <pre><code>StoreKit
  AudioToolbox
  MessageUI
  SystemConfiguration
  CoreGraphics
  AdSupport
  </code></pre>
  
  <p>And also use -ObjC link flags..</p>
  
  <p>What is the problem?</p>
  
  <p>Thanks!</p>