anchor.diff:  
     cfg = config.nix;
     daemon = config.services.nix-daemon;
  +
  +  buildHook = if versionAtLeast (cfg.package.version or "<unknown>") "1.12pre"
  +    then "build-remote" else "build-remote.pl";
   
     nixConf =
       let
  
positive.code:       }
  
        // optionalAttrs cfg.distributedBuilds {
          NIX_BUILD_HOOK = "${cfg.package}/libexec/nix/build-remote.pl";
          NIX_REMOTE_SYSTEMS = "/etc/nix/machines";
          NIX_CURRENT_LOAD = "/run/nix/current-load";
        };
  
negative.code:     environment.etc."nix/nix.conf".source = nixConf;
  
      # List of machines for distributed Nix builds in the format
      # expected by build-remote.
      environment.etc."nix/machines" =
        { enable = cfg.buildMachines != [];
          text =
  