Merge pull request #281658 from felipeqq2/legendary-gl/main-program

legendary-gl: add main program

pkgs/games/legendary-gl/default.nix

···
     homepage = "https://github.com/derrod/legendary";
     license = licenses.gpl3;
     maintainers = with maintainers; [ equirosa ];
+    mainProgram = "legendary";
   };
 
   passthru.updateScript = gitUpdater { };