fix: don't add local cache to builder

common/modules/cachix.nix

@@ -1,8 +1,11 @@
 {
   config,
+  lib,
   pkgs,
   ...
-}: {
+}: let
+  inherit (lib) optionals;
+in {
   environment.systemPackages = [
     (pkgs.writeShellApplication {
       name = "rebuild-no-cache";
@@ -15,22 +18,25 @@
 
   nix = {
     settings = {
-      substituters = [
-        "https://hyprland.cachix.org"
-        "https://nix-gaming.cachix.org"
-        # Nixpkgs-Wayland
-        "https://cache.nixos.org"
-        "https://nixpkgs-wayland.cachix.org"
-        "https://nix-community.cachix.org"
-        # Nix-community
-        "https://nix-community.cachix.org"
-        # Nh
-        "https://viperml.cachix.org"
-        # Caddy
-        "https://caddycf.cachix.org"
-        # Personal config cache
-        "https://cache.nelim.org"
-      ];
+      substituters =
+        [
+          "https://hyprland.cachix.org"
+          "https://nix-gaming.cachix.org"
+          # Nixpkgs-Wayland
+          "https://cache.nixos.org"
+          "https://nixpkgs-wayland.cachix.org"
+          "https://nix-community.cachix.org"
+          # Nix-community
+          "https://nix-community.cachix.org"
+          # Nh
+          "https://viperml.cachix.org"
+          # Caddy
+          "https://caddycf.cachix.org"
+        ]
+        ++ optionals (!config.services.nix-serve.enable) [
+          # Personal config cache
+          "https://cache.nelim.org"
+        ];
       trusted-public-keys = [
         "hyprland.cachix.org-1:a7pgxzMz7+chwVL3/pzj6jIBMioiJM7ypFP8PwtkuGc="
         "nix-gaming.cachix.org-1:nbjlureqMbRAxR1gJ/f3hxemL9svXaZF/Ees8vCUUs4="