Request flag for avoiding installation of dependencies

[BerendWijers]

I've been using the vol2bird installer on the Lisa cluster. Initially vol2birdinstall attempted to run sudo apt get update which prompts me for a sudo account. As the Lisa cluster does not allow the usage of Sudo I would like the ability to prevent having the installer updating libraries / apt. The Lisa cluster managers their libraries with modules and does not allow for apt usage.

We've disabled (uncommented) the lines in the installer script and managed to install just fine with loading the relevant libraries through modules