Fix platform name

flake.nix

@@ -75,7 +75,7 @@
               };
               "${package}_x86_64-apple" = import ./modules/holochain-cross.nix {
                 inherit localSystem inputs crate package;
-                crossSystem = "x86-64-darwin";
+                crossSystem = "x86_64-darwin";
                 rustTargetTriple = "x86_64-apple-darwin";
               };
             } else { });