add default julia_depot for kernel spec
right now, inside:
/cvmfs/sft-nightlies.cern.ch/lcg/views/dev4/Fri/x86_64-centos7-gcc10-opt/share/jupyter/kernels/julia-1.7/kernel.json
we have:
33 JULIA_DEPOT_PATH: /cvmfs/sft-nightlies.cern.ch/lcg/latest/jl_ijulia/1.23.2-e1360/x86_64-centos7-gcc10-opt/share/julia:/cvmfs/sft-nightlies.cern.ch/lcg/latest/julia/1.7.1-afc1c/x86_64-centos7-gcc10-opt/share/julia",
this is problematic as demonstrated earlier. I think it's the best idea to keep first entry in DEPOT_PATH always writeable, since IJulia will need to be recompiled if one of its dependencies gets updated by user.