Changed flake to use flake-utils and build for all targets

flake.nix

@@ -2,24 +2,26 @@
   description = "a lisp interpreter/compiler in ocaml";
   inputs =  {
     nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
   };
 
-  outputs = {self, nixpkgs}: 
+  outputs = {self, nixpkgs, flake-utils}:
+    flake-utils.lib.eachDefaultSystem (system:
   let
-    pkgs = nixpkgs.legacyPackages.x86_64-linux;
+    pkgs = nixpkgs.legacyPackages.${system};
     devInputs = with pkgs.ocamlPackages; [merlin];
     ocamlPkgs = with pkgs.ocamlPackages; [menhir dune_3];
     nativeInputs =  with pkgs; ocamlPkgs ++ [ocaml]; 
   in
   {
-    packages.x86_64-linux.default = pkgs.ocamlPackages.buildDunePackage {
+    packages.default = pkgs.ocamlPackages.buildDunePackage {
       pname = "ollisp";
       version = "0.0.1";
       src = pkgs.lib.cleanSource ./.;
       nativeBuildInputs = nativeInputs;
     };
-    devShells.x86_64-linux.default = pkgs.mkShell {
+    devShells.default = pkgs.mkShell {
       nativeBuildInputs = nativeInputs ++ devInputs;
     };
-  };
+  });
 }