Summary: [packer] Fix packlist Test Plan: Pull Request resolved: https://github.com/facebook/flipper/pull/5242 Imported from GitHub, without a `Test Plan:` line. Reviewed By: mweststrate Differential Revision: D50596825 Pulled By: passy fbshipit-source-id: be4f80f95be27f86aa61384f9dd46540bf4aa349