Currently there's a hard minimum version of Xcode that the tool supports, and if you're on an older version the tool doesn't let you build darwin project. It would be nice to track a minimum recommended version of Xcode that prompts a soft doctor warning to give users heads up to update their environments and CI systems before we bump the hard minimum. See CocoaPods minimum recommended version for implementation details.

We will need to require Xcode 12 soon, and it may be more palatable if that's not a surprise and we warn Xcode 12 is recommended now.