By "install packages" I mean to evaluate Nix build expressions (using nix-env, nix-shell -p, etc.) to build from source instead of using a substitute.
Originally posted on Stackoverflow but [Charles Duffy pointed it out][3] that it is more fitting to be here if itss about command-line tools or configuration. Still leaving it there because I assume forcing a package to always compile from source is possible by using the Nix language itself, I just don't yet know how. (Or if it is in fact not possible, someone will point it out, and then this question does belong here.)