This is a test issue, likely that the test was broken by a change in userspace.
The test creates a squashfs using /bin as the source. In disco this is a link to usr/bin, so the created squashfs contains a single file /bin which is also a symlink to usr/bin. Since this is a relative symlink and usr/bin doesn't exist in the squashfs, the attempt to diff the contents of /bin and $SQUASHFS_MNT/bin finds many differences, causing the test to fail.
This is a test issue, likely that the test was broken by a change in userspace.
The test creates a squashfs using /bin as the source. In disco this is a link to usr/bin, so the created squashfs contains a single file /bin which is also a symlink to usr/bin. Since this is a relative symlink and usr/bin doesn't exist in the squashfs, the attempt to diff the contents of /bin and $SQUASHFS_MNT/bin finds many differences, causing the test to fail.