objective-c - apple mach-o linker error, showing after xcode 4 -> 5 upgrade

Question

I'm trying to fix the errors below, they started coming up after I updated to XCode 5. Any idea how to resolve this error. I've looked in the Build Settings - Library Search Paths and its not listed there.

Undefined symbols for architecture armv7:
  "_GKPlayerAuthenticationDidChangeNotificationName", referenced from:
      -[DDGameKitHelper registerForLocalPlayerAuthChange] in DDGameKitHelper.o
  "_OBJC_CLASS_$_GKAchievementViewController", referenced from:
      objc-class-ref in DDGameKitHelper.o
  "_OBJC_CLASS_$_GKNotificationBanner", referenced from:
      objc-class-ref in GKAchievementHandler.o
      objc-class-ref in GKAchievementNotification.o
  "_OBJC_CLASS_$_GKLeaderboardViewController", referenced from:
      objc-class-ref in DDGameKitHelper.o
  "_OBJC_CLASS_$_GKAchievementDescription", referenced from:
      objc-class-ref in DDGameKitHelper.o
  "_OBJC_CLASS_$_GKAchievement", referenced from:
      objc-class-ref in DDGameKitHelper.o
     (maybe you meant: _OBJC_CLASS_$_GKAchievementNotification, _OBJC_CLASS_$_GKAchievementHandler )
  "_OBJC_CLASS_$_GKScore", referenced from:
      objc-class-ref in DDGameKitHelper.o
  "_OBJC_CLASS_$_GKLeaderboard", referenced from:
      objc-class-ref in DDGameKitHelper.o
  "_OBJC_CLASS_$_GKLocalPlayer", referenced from:
      objc-class-ref in DDGameKitHelper.o
ld: symbol(s) not found for architecture armv7
clang: error: linker command failed with exit code 1 (use -v to see invocation)