Error when running `bin/setup`

[terrablue]

This is related to #341

When running bin/setup as a normal user, I get the following error:

bundle install
+ bundle install
Fetching gem metadata from https://rubygems.org/.............
Resolving dependencies...
Bundler::PermissionError: There was an error while trying to write to `/usr/lib/ruby/gems/3.0.0/cache`. It is likely that you need to grant write
permissions for that path.
  /usr/lib/ruby/3.0.0/bundler/shared_helpers.rb:105:in `rescue in filesystem_access'

Trying to run it with sudo, I am advised not to do so:

Don't run Bundler as root. Installing your bundle as root will break this application for all non-root users on this machine.

What would be the way forward here?