fix(qemu): Persist /var/lib/libvirt

modules/nixos/qemu.nix

@@ -17,6 +17,11 @@ in {
           "$@"
       '';
     in {
+      sydnix.impermanence.directories = [
+        # Most importantly, stores images and disks.
+        "/var/lib/libvirt"
+      ];
+
       programs.virt-manager.enable = true;
 
       environment.systemPackages = [