e8ddba2bcf
This is already covered in the previous chapter https://github.com/NixOS/nixpkgs/blob/master/nixos/doc/manual/configuration/x-windows.xml#L38-L46 - Xfce also depends on X and it doesn't need a special section on display managers.
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.