Preserve file system compression when applying delta updates

[zorgiepoo]

If the new update has file system compression applied to its app bundle, we re-apply file system compression after applying our delta patch and before final verification.

I will add documentation update later for how to preserve file system compressions for normal updates (use .tar.* or .dmg and use ditto --hfsCompression beforehand).

Fixes #1194

Misc Checklist:

• My change requires a documentation update on Sparkle's website repository
• My change requires changes to generate_appcast, generate_keys, or sign_update

Only bug fixes to regressions or security fixes are being backported to the 1.x (master) branch now. If you believe your change is significant enough to backport, please also create a separate pull request against the master branch.

Testing

I tested and verified my change by using one or multiple of these methods:

• Sparkle Test App
• Unit Tests
• My own app
• Other (please specify)

Added unit tests to ensure file system compression is preserved on a large file. Tested test app with delta updates with some manual adjustments.

macOS version tested: 12.1 (21C52)