nixosTests: fix pure eval by setting system to null

nixos/tests/boot.nix

@@ -65,6 +65,7 @@ let
 
   iso =
     (import ../lib/eval-config.nix {
+      system = null;
       modules = [
         ../modules/installer/cd-dvd/installation-cd-minimal.nix
         ../modules/testing/test-instrumentation.nix
@@ -74,6 +75,7 @@ let
 
   sd =
     (import ../lib/eval-config.nix {
+      system = null;
       modules = [
         ../modules/installer/sd-card/sd-image-x86_64.nix
         ../modules/testing/test-instrumentation.nix
@@ -111,6 +113,7 @@ let
     let
       config =
         (import ../lib/eval-config.nix {
+          system = null;
           modules = [
             ../modules/installer/netboot/netboot.nix
             ../modules/testing/test-instrumentation.nix

nixos/tests/ec2.nix

@@ -12,6 +12,7 @@ with import common/ec2.nix { inherit makeTest pkgs; };
 let
   imageCfg =
     (import ../lib/eval-config.nix {
+      system = null;
       modules = [
         ../maintainers/scripts/ec2/amazon-image.nix
         ../modules/testing/test-instrumentation.nix

nixos/tests/image-contents.nix

@@ -14,6 +14,7 @@ with import common/ec2.nix { inherit makeTest pkgs; };
 let
   config =
     (import ../lib/eval-config.nix {
+      system = null;
       modules = [
         ../modules/testing/test-instrumentation.nix
         ../modules/profiles/qemu-guest.nix

nixos/tests/openstack-image.nix

@@ -12,6 +12,7 @@ with import common/ec2.nix { inherit makeTest pkgs; };
 let
   image =
     (import ../lib/eval-config.nix {
+      system = null;
       modules = [
         ../maintainers/scripts/openstack/openstack-image.nix
         ../modules/testing/test-instrumentation.nix

nixos/tests/systemd-machinectl.nix

@@ -26,6 +26,7 @@ import ./make-test-python.nix (
 
     containerSystem =
       (import ../lib/eval-config.nix {
+        system = null;
         modules = [ container ];
       }).config.system.build.toplevel;