[Chore] Fix tests evaluation and build

Author: rvem

nix/tests/common.nix

@@ -15,6 +15,7 @@
     };
   };
 
+  system.switch.enable = true;
   virtualisation.graphics = false;
   virtualisation.memorySize = 1536;
   boot.loader.grub.enable = false;

nix/tests/default.nix

@@ -9,7 +9,7 @@ let
   inherit (import "${pkgs.path}/nixos/tests/ssh-keys.nix" pkgs) snakeOilPrivateKey;
 
   # Include all build dependencies to be able to build profiles offline
-  allDrvOutputs = pkg: pkgs.runCommand "allDrvOutputs" { refs = pkgs.writeReferencesToFile pkg.drvPath; } ''
+  allDrvOutputs = pkg: pkgs.runCommand "allDrvOutputs" { refs = pkgs.writeClosure pkg.drvPath; } ''
     touch $out
     while read ref; do
       case $ref in