Preserve folders between builds

Our project uses Carthage for dependency management and is set to --cache-builds so that it doesn't need to completely rebuild dependencies on each build. A bot run by Xcode Server appears to do a clean operation before each build (the job is explicitly set to never clean), which nukes the Carthage folder at the beginning of each build. This greatly increase the build time since each framework has to be rebuilt. What, if anything, can I do to prevent the Bot from deleting this directory at the beginning of the build?


Thanks,

Bob