treewide: fix loss of precision in NixOS systems

Prior to this patch:

	$ nix-instantiate --eval -E '
	>   with import ./. {
	>     localSystem.config = "aarch64-unknown-linux-musl";
	>   };
	>   (nixos {}).config.nixpkgs.localSystem.config
	> '
	"aarch64-unknown-linux-gnu"

Because only the system triple was being passed through, the Musl part
of the system specification was lost.  This patch fixes various
occurrences of NixOS evaluation when a Nixpkgs evaluation is already
available, to pass through the full elaborated system attribute set,
to avoid this loss of precision.

1 files changed, 2 insertions, 1 deletions

diff --git a/nixos/tests/containers-imperative.nix b/nixos/tests/containers-imperative.nix
index a21ce97a23b15..3007efaf88710 100644
--- a/nixos/tests/containers-imperative.nix
+++ b/nixos/tests/containers-imperative.nix
@@ -18,8 +18,9 @@ import ./make-test-python.nix ({ pkgs, lib, ... }: {
       # container available within the VM, because we don't have network access.
       virtualisation.additionalPaths = let
         emptyContainer = import ../lib/eval-config.nix {
-          inherit (config.nixpkgs.localSystem) system;
           modules = lib.singleton {
+            nixpkgs = { inherit (config.nixpkgs) localSystem; };
+
             containers.foo.config = {
               system.stateVersion = "18.03";
             };