Metadata for directories inside the squashfs not reproducible in some environments

See #12608-note_18 for arnaud’s diffoscope report. There are also .torrent:s for the good ISO, and for arnaud’s.

The diffs all look like this:

│ │  -rwxr-xr-x root/root              3499 2016-11-13 23:23 /usr/lib/gnupg1/gpgkeys_mailto
│ │ -drwxr-xr-x root/root                90 2017-05-21 18:33 /usr/lib/gnupg2
│ │ +drwxr-xr-x root/root               102 2017-05-21 18:33 /usr/lib/gnupg2
│ │  lrwxrwxrwx root/root                30 2017-02-14 00:29 /usr/lib/gnupg2/gpg-preset-passphrase -> ../gnupg/gpg-preset-passphrase

Parent Task: #5630 (closed)

Original created by @anonym on 12739 (Redmine)