python3Packages.kicad: mark broken on Darwin (#403987)

pkgs/applications/science/electronics/kicad/base.nix

···
     homepage = "https://www.kicad.org/";
     license = lib.licenses.gpl3Plus;
     platforms = lib.platforms.all;
+    broken = stdenv.hostPlatform.isDarwin;
   };
 }