Support for buildable folders in generated projects

Apple introduced buildable folders in Xcode 16 to reduce git conflicts in .pbxproj files. While we initially postponed support since these conflicts weren't frequent in our workflow, user feedback revealed another compelling benefit: buildable folders eliminate the need to regenerate projects when files are added outside of Xcode's UI—particularly valuable for automated agents and CI/CD pipelines.

Based on this feedback, we've now added support for buildable folders. If you're currently using Target.sources and Target.resources, you can migrate to the new Target.buildableFolders property to define buildable folders for your targets.

Note: Xcode's synchronized groups (the underlying implementation of buildable folders) support "exceptions"—files or folders that can be excluded from synchronization. While we don't support exceptions yet, we'll add this feature based on user demand.