top-level: return __splicedPackages

nixos/lib/testing/driver.nix

@@ -202,7 +202,7 @@ in
     _module.args = {
       hostPkgs =
         # Comment is in nixos/modules/misc/nixpkgs.nix
-        lib.mkOverride lib.modules.defaultOverridePriority config.hostPkgs.__splicedPackages;
+        lib.mkOverride lib.modules.defaultOverridePriority config.hostPkgs;
     };
 
     driver = withChecks driver;

nixos/modules/misc/nixpkgs.nix

@@ -355,7 +355,7 @@ in
         # which is somewhat costly for Nixpkgs. With an explicit priority, we only
         # evaluate the wrapper to find out that the priority is lower, and then we
         # don't need to evaluate `finalPkgs`.
-        lib.mkOverride lib.modules.defaultOverridePriority finalPkgs.__splicedPackages;
+        lib.mkOverride lib.modules.defaultOverridePriority finalPkgs;
     };
 
     assertions =

nixos/modules/misc/nixpkgs/read-only.nix

@@ -63,7 +63,7 @@ in
       # find mistaken definitions
       builtins.seq cfg.config builtins.seq cfg.overlays builtins.seq cfg.hostPlatform builtins.seq
         cfg.buildPlatform
-        cfg.pkgs.__splicedPackages;
+        cfg.pkgs;
     nixpkgs.config = cfg.pkgs.config;
     nixpkgs.overlays = cfg.pkgs.overlays;
     nixpkgs.hostPlatform = cfg.pkgs.stdenv.hostPlatform;

pkgs/stdenv/booter.nix

@@ -162,5 +162,9 @@ let
         buildPackages.stdenv.cc;
   };
 
+  pkgs = dfold folder postStage (_: { }) withAllowCustomOverrides;
+
 in
-dfold folder postStage (_: { }) withAllowCustomOverrides
+# Return the spliced package set, so that consumers of the nixpkgs top-level
+# attributes, like NixOS, don't break when cross-compiling.
+pkgs.__splicedPackages