This code is only run on IUKs generated on the fly by this test suite,
with filenames like "A" and "B", so this is a no-op at the moment.

But if ever introduce filenames with spaces, then the previous code would fail
because the output of `rdsquashfs` would look like this:

    file "etc/NetworkManager/system-connections/Wired connection" 0600 0 0