Add basic binary cache stuff

flake.nix

@@ -198,6 +198,7 @@
           self.nixosModules.basics
           ./system/elysia-clarki.nix
           ./system/elysia-clarki-hardware.nix
+          ./system/modules/binary-cache.nix
 
           ({ pkgs, ... }: {
             # Override kernel version for zfs

system/modules/binary-cache.nix

@@ -0,0 +1,8 @@
+{ pkgs, ... }:
+
+{
+  services.nix-serve = {
+    enable = true;
+    secretKeyFile = "/var/cache-priv-key.pem";
+  };
+}