Fix interaction between appendOverlays and otherPackageSets

The comment

    a dirty hack that should be removed

has led me to believe that nixpkgsFun isn't the right solution,
but bypassing it is worse, because it creates a second, inner
overriding mechanism that doesn't pass its changes to the old,
outer overriding mechanism.

Before this change:

    nix-repl> ((import <nixpkgs> {}).appendOverlays([(f: s: { foobarbaz = "ok"; })])).foobarbaz
    "ok"

    nix-repl> ((import <nixpkgs> {}).appendOverlays([(f: s: { foobarbaz = "ok"; })])).pkgsCross.aarch64-multiplatform.foobarbaz
    error: attribute 'foobarbaz' missing

           at «string»:1:1:

                1| ((import <nixpkgs> {}).appendOverlays([(f: s: { foobarbaz = "ok"; })])).pkgsCross.aarch64-multiplatform.foobarbaz
                 | ^
                2|

After this change:

    nix-repl> ((import ./. {}).appendOverlays([(f: s: { foobarbaz = "ok"; })])).pkgsCross.aarch64-multiplatform.foobarbaz
    "ok"

Thanks to samueldr for discovering this problem.

0 files changed, 0 insertions, 0 deletions