move stuff out of /sys/profiles/*/default.nix

sys/profiles/nix/nix.nix

@@ -0,0 +1,50 @@
+{inputs, ...}: {
+  nix = {
+    registry.nixpkgs.to = {
+      type = "github";
+      owner = "NixOS";
+      repo = "nixpkgs";
+      rev = inputs.nixpkgs.rev;
+    };
+
+    nixPath = ["nixpkgs=${inputs.nixpkgs.outPath}"];
+
+    settings = {
+      builders-use-substitutes = true;
+      keep-outputs = true;
+      keep-derivations = true;
+      accept-flake-config = true;
+      use-xdg-base-directories = true;
+
+      flake-registry = builtins.toFile "none.json" (builtins.toJSON {
+        flakes = [];
+        version = 2;
+      });
+
+      experimental-features = [
+        "flakes"
+        "nix-command"
+        "pipe-operators"
+        "no-url-literals"
+        "ca-derivations"
+      ];
+
+      trusted-users = [
+        "root"
+        "@wheel"
+      ];
+
+      substituters = [
+        "https://cache.nixos.org?priority=10"
+        "https://nix-community.cachix.org?priority=11"
+        "https://nix-gaming.cachix.org?priority=12"
+      ];
+
+      trusted-public-keys = [
+        "cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY="
+        "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs="
+        "nix-gaming.cachix.org-1:nbjlureqMbRAxR1gJ/f3hxemL9svXaZF/Ees8vCUUs4="
+      ];
+    };
+  };
+}