systemd-lib: cleanup empty lines in unit files

  serviceToUnit = name: def:

    { inherit (def) aliases wantedBy requiredBy enable overrideStrategy;

      text = commonUnitText def +

        ''

      text = commonUnitText def + ''

        [Service]

          ${let env = cfg.globalEnvironment // def.environment;

      '' + (let env = cfg.globalEnvironment // def.environment;

        in concatMapStrings (n:

          let s = optionalString (env.${n} != null)

            "Environment=${builtins.toJSON "${n}=${env.${n}}"}\n";

          # systemd max line length is now 1MiB

          # https://github.com/systemd/systemd/commit/e6dde451a51dc5aaa7f4d98d39b8fe735f73d2af

              in if stringLength s >= 1048576 then throw "The value of the environment variable ‘${n}’ in systemd service ‘${name}.service’ is too long." else s) (attrNames env)}

          ${if def ? reloadIfChanged && def.reloadIfChanged then ''

          in if stringLength s >= 1048576 then throw "The value of the environment variable ‘${n}’ in systemd service ‘${name}.service’ is too long." else s) (attrNames env))

      + (if def ? reloadIfChanged && def.reloadIfChanged then ''

        X-ReloadIfChanged=true

      '' else if (def ? restartIfChanged && !def.restartIfChanged) then ''

        X-RestartIfChanged=false

          '' else ""}

          ${optionalString (def ? stopIfChanged && !def.stopIfChanged) "X-StopIfChanged=false"}

          ${attrsToSection def.serviceConfig}

        '';

      '' else "")

       + optionalString (def ? stopIfChanged && !def.stopIfChanged) ''

         X-StopIfChanged=false

      '' + attrsToSection def.serviceConfig;

    };

  socketToUnit = name: def: