Please update your Apple SDK location in Visual Studio's preferences (Projects > SDK Locations > Apple > Apple SDK). Library/Frameworks/amework/External/xbuild/Xamarin/Mac/(3,3): Error: Could not find a valid Xcode app bundle at '/Applications/Xcode.app/Contents/Developer/'. I just updated visual Studio for Mac to 8.8 (build 1651) and now I'm getting this build error.
