--derivation
It doesn't do anything here, and in the next commit `show-derivation will no longer accept this flag.
Make sure that their timestamp are always normalized. Otherwise, strange − and non-deterministic − things might happen, like https://github.com/NixOS/nixpkgs/issues/121813 Fix #4775
Requires a slight update to the test infra to work properly, but having the possibility to group tests that way makes the whole thing quite cleaner imho
