eacd1b75dc
It seems as the sentence at the bottom of the option summary about Nix-specific options isn't enough, it's probably more helpful to list those options in the synopsis as well.
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.