Merge pull request #218779 from viraptor/fiddle-deps

rubyPackages.fiddle: add libffi to dependencies

pkgs/development/ruby-modules/gem-config/default.nix

···
     buildInputs = [ libffi ];
   };
 
+  fiddle = attrs: {
+    buildInputs = [ libffi ];
+  };
+
   gdk_pixbuf2 = attrs: {
     nativeBuildInputs = [ pkg-config bundler rake ]
       ++ lib.optionals stdenv.isDarwin [ DarwinTools ];