fix distributed user setup in remote machine

hosts/common/optional/distributed_builds/remote-builder-machine.nix

@@ -1,24 +1,15 @@
-{ pkgs, configVars, ... }:
-let
-  remoteBuilderIp = configVars.networking.addresses.remote-builder.ip;
-in
 {
-  nix.distributedBuilds = true;
-  nix.settings.builders-use-substitutes = true;
+  users.users.remotebuild = {
+    isNormalUser = true;
+    createHome = false;
+    group = "remotebuild";
 
-  nix.buildMachines = [
-    {
-      hostName = remoteBuilderIp;
-      sshUser = "remotebuild";
-      sshKey = "/root/.ssh/remotebuild";
-      system = pkgs.stdenv.hostPlatform.system;
-      supportedFeatures = [ "nixos-test" "big-parallel" "kvm" ];
-    }
-  ];
-
-  sops.secrets = {
-    "ssh_keys/root/remotebuild" = {
-      path = "/root/.ssh/remotebuild";
-    };
+    openssh.authorizedKeys.keyFiles = [
+      ./remotebuild.pub
+    ];
   };
+
+  users.groups.remotebuild = {};
+
+  nix.settings.trusted-users = ["remotebuild"];
 }