This reverts commit fb6d63f3fd.
I really hope this finally fixes #99236: evaluation on Hydra.
This time I really did check basically the same commit on Hydra:
https://hydra.nixos.org/eval/1618011
Right now I don't have energy to find what exactly is wrong in the
commit, and it doesn't seem important in comparison to nixos-unstable
channel being stuck on a commit over one week old.
To build the manual, you need Nix installed on your system (no need
for NixOS). To install Nix, follow the instructions at
https://nixos.org/nix/download.html
When you have Nix on your system, in the root directory of the project
(i.e., `nixpkgs`), run:
nix-build nixos/release.nix -A manual.x86_64-linux
When this command successfully finishes, it will tell you where the
manual got generated.