flake: drop flake-utils as a dependency

Replace flake-utils with a few lines of pure nix code, since flake-utils
is not really useful here.

flake.lock

@@ -1,23 +1,5 @@
 {
   "nodes": {
-    "flake-utils": {
-      "inputs": {
-        "systems": "systems"
-      },
-      "locked": {
-        "lastModified": 1710146030,
-        "narHash": "sha256-SZ5L6eA7HJ/nmkzGG7/ISclqe6oZdOZTNoesiInkXPQ=",
-        "owner": "numtide",
-        "repo": "flake-utils",
-        "rev": "b1d9ab70662946ef0850d488da1c9019f3a9752a",
-        "type": "github"
-      },
-      "original": {
-        "owner": "numtide",
-        "repo": "flake-utils",
-        "type": "github"
-      }
-    },
     "nixpkgs": {
       "locked": {
         "lastModified": 1725036679,
@@ -36,24 +18,8 @@
     },
     "root": {
       "inputs": {
-        "flake-utils": "flake-utils",
         "nixpkgs": "nixpkgs"
       }
-    },
-    "systems": {
-      "locked": {
-        "lastModified": 1681028828,
-        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
-        "owner": "nix-systems",
-        "repo": "default",
-        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
-        "type": "github"
-      },
-      "original": {
-        "owner": "nix-systems",
-        "repo": "default",
-        "type": "github"
-      }
     }
   },
   "root": "root",

flake.nix

@@ -1,17 +1,19 @@
 {
   description = "YaCy -- distributed search engine";
   inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
-  inputs.flake-utils.url = "github:numtide/flake-utils";
 
-  outputs = { self, nixpkgs, flake-utils }:
-    flake-utils.lib.eachDefaultSystem (system: let
-      pkgs = nixpkgs.legacyPackages.${system};
-    in {
-      devShells.default = pkgs.mkShell {
-        packages = [
-            pkgs.ant
-            pkgs.temurin-bin-11
+  outputs = inputs: let
+    systems = ["x86_64-linux" "aarch64-linux" "x86_64-darwin" "aarch64-darwin"];
+    forEachSystem = inputs.nixpkgs.lib.genAttrs systems;
+    pkgsForEach = inputs.nixpkgs.legacyPackages;
+  in {
+    devShells = forEachSystem (system: {
+      default = pkgsForEach.${system}.mkShell {
+        packages = with pkgsForEach.${system}; [
+          pkgs.ant
+          pkgs.temurin-bin-11
         ];
       };
     });
+  };
 }