Investigate checksum diff between original and repacked .pkg files

[ellahathaway]

See #15205 (comment)

The checksums are different between the original and repacked .pkgs. After briefly investigating this, I've found that the Bom file has a different checksum and the Payload tarball is bigger in the repacked .pkg than the original .pkgs.

We should spend time looking into this to determine the cause of the issue.