add(cachix): faster installation of system

modules/system/default.nix

@@ -1,6 +1,7 @@
 {pkgs, ...}: {
   imports = [
     ../../system/time.nix
+    ../../system/nix.nix
     ../../system/backlight.nix
     ../../system/boot.nix
     ../../system/amd.nix
@@ -19,5 +20,6 @@
     # FIXME: must be on their own app
     git
     cloudflared
+    cachix
   ];
 }

system/nix.nix

@@ -0,0 +1,15 @@
+{pkgs, ...}: {
+  nix.settings = {
+    substituters = [
+      "https://cache.nixos.org"
+      "https://hyprland.cachix.org"
+      "https://nix-community.cachix.org"
+    ];
+    trusted-public-keys = [
+      "cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY="
+      "hyprland.cachix.org-1:a7pgxzMz7+chwVL3/pzj6jIBMioiJM7ypFP8PwtkuGc="
+      "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs="
+    ];
+    experimental-features = ["nix-command" "flakes"];
+  };
+}

system/version.nix

@@ -5,7 +5,6 @@
     distributedBuilds = true;
     settings = {
       builders-use-substitutes = true;
-      experimental-features = ["nix-command" "flakes"];
     };
   };
 }