Fix bugs related to mismatched / missing nix

nixos/modules/containers.nix

@@ -198,7 +198,7 @@ in
             ''
               if [ ! -e "${sysProfile}" ]; then
                 echo "Creating dummy profile"
-                ${pkgs.nix}/bin/nix-env -p ${sysProfile} --set ${dummyProfile}
+                ${config.nix.package}/bin/nix-env -p ${sysProfile} --set ${dummyProfile}
               fi
             ''}
 

nixos/modules/deploy-rs.nix

@@ -9,7 +9,7 @@ let
   keepGensOpt = with lib.types; mkOpt' ints.unsigned 10
     "Number of generations to keep when cleaning up old deployments (0 to disable deletion on deployment).";
   keepGensSnippet = p: n: optionalString (n > 0) ''
-    ${pkgs.nix}/bin/nix-env -p "${p}" --delete-generations +${toString n}
+    ${config.nix.package}/bin/nix-env -p "${p}" --delete-generations +${toString n}
   '';
 
   # Based on https://github.com/serokell/deploy-rs/blob/master/flake.nix