call SDL_Quit() before exit(0) (linux window closing issue) (#408)

* use _Exit(0) on linux

* use SDL_Quit() instead of _Exit(0)

* remove unnecessary call, add bandaid comment

Co-authored-by: briaguya <briaguya@alice>

libultraship/libultraship/Lib/Fast3D/gfx_sdl2.cpp

@@ -249,6 +249,7 @@ static void gfx_sdl_handle_events(void) {
                 }
                 break;
             case SDL_QUIT:
+                SDL_Quit(); // bandaid fix for linux window closing issue
                 exit(0);
         }
     }