title: Xcode SDK Version Issue
body: <p>I'm having a bit of an issue with distributing an app via the latest version of Xcode (Version 10.1 (10B61)).  Every time I try to upload it to the App Store via organizer, I get this error after uploading: </p>
  
  <p><code>WARNING ITMS-90725: "SDK Version Issue. This app was built with the iOS 12.0 SDK. Starting March 2019, all iOS apps submitted to the App Store must be built with the iOS 12.1 SDK or later, included in Xcode 10.1 or later."</code></p>
  
  <p>Previous answers to this question said that it was just a warning and that I should still be able to upload my app, but it is now March and I am still getting the error even on 10.1.  iTunesConnect will not let me select these builds and I get emails about the validation failure.</p>
  
  <p>Further details:</p>
  
  <pre><code>-The app is an iMessage extension, and uses exactly 1 framework from Carthage, which is up to date with the latest framework version and Carthage version.
  -My project and Message extension targets Swift Language Version build setting is Swift 4.2.
  -My deployment target is iOS 11.0, but the issue persists after selecting iOS 12.1.
  -The app compiles and runs fine on my physical device running iOS 12.1.
  -The issue persists after a build folder clean.
  -The issue persists after reinstalling Xcode.
  </code></pre>
  
  <p>If anyone has any suggestions as to how I can verify my app is compiling with the latest SDK please let me know.</p>