fix missing gfortran lib on Mac+Nix

Author: bbyalcinkaya

flake.nix

@@ -72,6 +72,9 @@
             });
           groups = [ ];
           checkGroups = [ ];
+          
+          # Add gfortran on macOS to ensure libgfortran.x.dylib is in the runtime path
+          nativeBuildInputs = pkgs.lib.optionals pkgs.stdenv.isDarwin [ pkgs.gfortran ];
         };
 
         mkKomet = {komet-rust ? null, komet-stellar ? null}@args: pkgs.stdenv.mkDerivation {