refactor(nix): don't instantiate nixpkgs

See https://zimbatm.com/notes/1000-instances-of-nixpkgs

Signed-off-by: Sefa Eyeoglu <contact@scrumplex.net>

flake.nix

@@ -23,5 +23,17 @@
   outputs = inputs:
     inputs.flake-parts.lib.mkFlake
     {inherit inputs;}
-    {imports = [./nix];};
+    {
+      imports = [
+        ./nix/dev.nix
+        ./nix/distribution.nix
+      ];
+
+      systems = [
+        "x86_64-linux"
+        "aarch64-linux"
+        "x86_64-darwin"
+        "aarch64-darwin"
+      ];
+    };
 }