Detect changes to PBXCopyFilesBuildPhase during target build up-to-date checking

[lacasseio]

As a user building Xcode targets using Gradle, I want the Gradle tasks representing the Xcode targets using PBXCopyFilesBuildPhase to be out-of-date when its build specification change during an incremental build so I can have accurate feedback.

### Sub-Stories
- [ ] https://github.com/nokeedev/gradle-native/issues/788

Acceptance Criteria

• [x] Any changes to files, e.g. adding new items or removing existing items. ~Ordering change should have no effect.~(We decided against ignoring ordering)
• [x] Any changes to the files/directories represented by files.
• [ ] Any changes to the files/directories mapped by dstPath/dstSubfolderSpec from files. We track the individual files/directories copied over and not the destination path as a whole.