fix: relative link from epic-main to epic-git.<hash>_main
Instead of
$ ls -al /cvmfs/singularity.opensciencegrid.org/eicweb/jug_xl\:nightly/opt/detector/epic-main
lrwxrwxrwx 1 cvmfs cvmfs 68 Jun 3 14:36 /cvmfs/singularity.opensciencegrid.org/eicweb/jug_xl:nightly/opt/detector/epic-main -> /opt/detector/epic-git.8c40e0ba534f9c3bd7cac3bfcbb46c785b368643_main
this PR will result in
$ ls -al /cvmfs/singularity.opensciencegrid.org/eicweb/jug_xl\:nightly/opt/detector/epic-main
lrwxrwxrwx 1 cvmfs cvmfs 68 Jun 3 14:36 /cvmfs/singularity.opensciencegrid.org/eicweb/jug_xl:nightly/opt/detector/epic-main -> epic-git.8c40e0ba534f9c3bd7cac3bfcbb46c785b368643_main