components.nix: Extract dependency scope

This avoids polluting nixComponents with things that aren't our
components.
Fixes the extraction of passthru tests, which failed for boehmgc
which had many irrelevant ones anyway.

flake.nix

@@ -176,11 +176,21 @@
           # without "polluting" the top level "`pkgs`" attrset.
           # This also has the benefit of providing us with a distinct set of packages
           # we can iterate over.
-          nixComponents = lib.makeScope final.newScope (import ./packaging/components.nix {
+          nixComponents = lib.makeScope final.nixDependencies.newScope (import ./packaging/components.nix {
             pkgs = final;
             inherit stdenv versionSuffix;
           });
 
+          # The dependencies are in their own scope, so that they don't have to be
+          # in Nixpkgs top level `pkgs` or `nixComponents`.
+          nixDependencies = lib.makeScope final.newScope (scope: {
+            inherit stdenv versionSuffix;
+            libseccomp = final.libseccomp_nix;
+            boehmgc = final.boehmgc_nix;
+            libgit2 = final.libgit2_nix;
+            busybox-sandbox-shell = final.busybox-sandbox-shell or final.default-busybox-sandbox-shell;
+          });
+
           nix = final.nixComponents.nix;
 
           nix-internal-api-docs = final.callPackage ./src/internal-api-docs/package.nix {

packaging/components.nix

@@ -5,12 +5,6 @@ in
 
 # This becomes the pkgs.nixComponents attribute set
 {
-  inherit stdenv versionSuffix;
-  libseccomp = pkgs.libseccomp_nix;
-  boehmgc = pkgs.boehmgc_nix;
-  libgit2 = pkgs.libgit2_nix;
-  busybox-sandbox-shell = pkgs.busybox-sandbox-shell or pkgs.default-busybox-sandbox-shell;
-
   nix = callPackage ../package.nix { };
 
   nix-util = callPackage ../src/libutil/package.nix { };