top-level: Less indirection for lib in release*.nix

pkgs/top-level/release-cross.nix

···
-
 { # The platforms for which we build Nixpkgs.
   supportedSystems ? [ builtins.currentSystem ]
 , # Strip most of attributes when evaluating to spare memory usage
···
 with import ./release-lib.nix { inherit supportedSystems scrubJobs; };
 
 let
-  inherit (pkgs) lib;
-
   nativePlatforms = linux;
 
   /* Basic list of packages to cross-build */

pkgs/top-level/release-lib.nix

···
 , scrubJobs ? true
 }:
 
-with import ../../lib;
+let
+  lib = import ../../lib;
+in with lib;
 
 rec {
 
···
   });
 
   pkgs = pkgsFor "x86_64-linux";
+  inherit lib;
 
 
   hydraJob' = if scrubJobs then hydraJob else id;

pkgs/top-level/release-python.nix

···
    $ hydra-eval-jobs pkgs/top-level/release-python.nix
 */
 
-{ nixpkgs ? { outPath = (import ../.. {}).lib.cleanSource ../..; revCount = 1234; shortRev = "abcdef"; }
+{ nixpkgs ? { outPath = (import ../../lib).cleanSource ../..; revCount = 1234; shortRev = "abcdef"; }
 , officialRelease ? false
 , # The platforms for which we build Nixpkgs.
   supportedSystems ? [ "x86_64-linux" ]
 }:
 
-with import ../../lib;
 with import ./release-lib.nix {inherit supportedSystems; };
+with lib;
 
 let
   packagePython = mapAttrs (name: value:

pkgs/top-level/release-small.nix

···
 /* A small release file, with few packages to be built.  The aim is to reduce
    the load on Hydra when testing the `stdenv-updates' branch. */
 
-{ nixpkgs ? { outPath = (import ../.. {}).lib.cleanSource ../..; revCount = 1234; shortRev = "abcdef"; }
+{ nixpkgs ? { outPath = (import ../../lib).cleanSource ../..; revCount = 1234; shortRev = "abcdef"; }
 , supportedSystems ? [ "x86_64-linux" "i686-linux" "x86_64-darwin" ]
 }:
 

pkgs/top-level/release.nix

···
    $ nix-build pkgs/top-level/release.nix -A coreutils.x86_64-linux
 */
 
-{ nixpkgs ? { outPath = (import ../.. {}).lib.cleanSource ../..; revCount = 1234; shortRev = "abcdef"; }
+{ nixpkgs ? { outPath = (import ../../lib).cleanSource ../..; revCount = 1234; shortRev = "abcdef"; }
 , officialRelease ? false
 , # The platforms for which we build Nixpkgs.
   supportedSystems ? [ "x86_64-linux" "i686-linux" "x86_64-darwin" "aarch64-linux" ]
···
 with import ./release-lib.nix { inherit supportedSystems scrubJobs; };
 
 let
-
-  lib = pkgs.lib;
-
   jobs =
     { tarball = import ./make-tarball.nix { inherit pkgs nixpkgs officialRelease; };