Add remote builds (#4)

Reviewed-on: greyweather/nixos#4

hosts/kitagawa/default.nix

@@ -18,6 +18,26 @@ in {
     ./modules/hardware-fixes.nix
   ];
 
+  nix.buildMachines = [
+    {
+      hostName = "builder";
+      systems = [ "x86_64-linux" "i686-linux" ];
+      protocol = "ssh-ng";
+      maxJobs = 25;
+      speedFactor = 100;
+      supportedFeatures = [ "nixos-test" "benchmark" "kvm" "big-parallel" ];
+    }
+    {
+      hostName = "localhost";
+      systems = [ "x86_64-linux" "i686-linux" ];
+      maxJobs = 10;
+      speedFactor = 1;
+      supportedFeatures = [ ];
+    }
+  ];
+  nix.distributedBuilds = true;
+  nix.settings.builders-use-substitutes = true;
+
   services.tailscale = {
     enable = true;
     openFirewall = true;