squashdir.sh including leading path

[AlexandreHutton]

The squashdir.sh utility includes part of the path that shouldn't be present in output:

sbatch --account=rpp-aevans-ab --array=0 ../../../ukbm/slurm/squashdir.sh -d 3 -f 'neurohub_ukbb_t1w_bids_derivatives_ses3_${SLURM_ARRAY_TASK_ID}_bids.squashfs' 20252_3_0/neurohub

Leads to 20252_3_0 being included in the path: /20252_3_0/neurohub/

(Reported by @maxadam2017 )