Merge branch 'master' into closure-size

Beware that stdenv doesn't build. It seems something more will be needed
than just resolution of merge conflicts.

pkgs/test/mkOption/keep.nix

@@ -1,5 +1,5 @@
 let
-  pkgs = import ../../top-level/all-packages.nix {};
+  pkgs = import ../../.. {};
   config = import ./declare.nix;
 in
   with (pkgs.lib);

pkgs/test/mkOption/merge.nix

@@ -1,5 +1,5 @@
 let
-  pkgs = import ../../top-level/all-packages.nix {};
+  pkgs = import ../../.. {};
   config = import ./declare.nix;
 
   # Define the handler of unbound options.