When releasing an app-store version of an app from a beta Xcode stack the following error occurs:
ITMS-90111: Invalid Toolchain - Your app was built with a beta version of Xcode or SDK.
Beta Xcode stacks do not support uploading apps to the App Store. We recommend that you switch from beta to stable. Here is how:
1. On Bitrise go to your app and click the Workflow tab.
2. Click the Stack tab.
3. Check the Default Stack status to see which version your Workflow is running on. The first entry in the Default Stack dropdown is usually the latest beta version of Xcode available, while the second one is the latest stable.
4. Select a stable version instead of the beta one.
5. Save your changes and run a new build.