nixos/release.nix: Move forAllSystems to release-lib

There's already a similar forTheseSystems in release-lib, so be more
consistent.

nixos/release.nix

@@ -3,6 +3,7 @@
 , supportedSystems ? [ "x86_64-linux" "aarch64-linux" ]
 }:
 
+with import ../pkgs/top-level/release-lib.nix { inherit supportedSystems; };
 with import ../lib;
 
 let
@@ -11,8 +12,6 @@ let
   versionSuffix =
     (if stableBranch then "." else "pre") + "${toString nixpkgs.revCount}.${nixpkgs.shortRev}";
 
-  forAllSystems = genAttrs supportedSystems;
-
   importTest = fn: args: system: import fn ({
     inherit system;
   } // args);

pkgs/top-level/release-lib.nix

@@ -58,6 +58,7 @@ rec {
      interested in the result of cross building a package. */
   crossMaintainers = [ maintainers.viric ];
 
+  forAllSystems = genAttrs supportedSystems;
   forTheseSystems = systems: f:
     genAttrs (filter (x: elem x supportedSystems) systems) f;