Split derived data directory assembling into custom sync task

[lacasseio]

As a Nokee developer, I want to reduce the complexity of assembling the derived data directory so that it can use more Gradle features, i.e. InputChanges.

Acceptance Criteria

• Deleting a file from any input-derived data directory should be clear from the assembled derived data directory.
• Adding a file in any input-derived data directory should be added to the assembled derived data directory.
• Changes to files from any input-derived data directory synched to the assembled derived data directory.
• New files in the assembled derived data directory should not be removed in subsequent execution.

[lacasseio]

Just for completeness, we tried to share the same derived data directory throughout all build tasks, but Xcode locks a database which prevents concurrent builds from running.

[lacasseio]

Due to several issues with Gradle APIs, this task is more challenging than initially thought. It will bleed into the next iteration.