Map host keys into build-vms

lib/system.nix

@@ -18,6 +18,15 @@
                                 imports = [
                                     machineConfig
                                 ];
+
+                                virtualisation.vmVariant = {
+                                    virtualisation.sharedDirectories = {
+                                        keys = {
+                                            source = "/etc/ssh";
+                                            target = "/etc/ssh";
+                                        };
+                                    };
+                                };
                             })
                     ];
                 }