build: separated the nix flake and derivation, to allow for simpler builds and more flexibility

flake.nix

@@ -9,23 +9,8 @@
     flake-utils.lib.eachDefaultSystem (system:
   let
     pkgs = nixpkgs.legacyPackages.${system};
-    devInputs = with pkgs.ocamlPackages; [merlin];
-    ocamlPkgs = with pkgs.ocamlPackages; [menhir dune_3];
-    libs = with pkgs.ocamlPackages; [findlib];
-    nativeInputs =  with pkgs; ocamlPkgs ++ [ocaml];
   in
   {
-    packages.default = (pkgs.ocamlPackages.buildDunePackage {
-      pname = "ollisp";
-      version = "0.0.1";
-      src = pkgs.lib.cleanSource ./.;
-      nativeBuildInputs = nativeInputs;
-      buildInputs = libs;
-    });
-    
-    devShells.default = pkgs.mkShell {
-      nativeBuildInputs = nativeInputs ++ devInputs;
-      buildInputs = libs;
-    };
+    packages.default = pkgs.callPackage ./default.nix {};
   });
 }