The VoltBuilder servers are now using Xcode 13.0, the latest update from Apple. This allows you to build apps for iOS 15.0, which was released last week by Apple.
You don’t need to make any changes to your project to use the new release: all VoltBuilder jobs are now processed using it.
Before we went live with the new release, we tested by processing an entire day of iOS builds. They executed cleanly, with the same results as Xcode 12.4. We don’t anticipate any problems for you with the new release, but please let is know if you spot anything.
(The last version of Xcode supported by PhoneGap Build was 9.2.)