asciidoctor: disable epubcheck by default (#65018)
asciidoctor: disable epubcheck by default (#65018)

`epubcheck` pulls in Java, which can be problematic on some platforms,
and some fairly core software uses asciidoctor to build docs.
NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs