A variable that lets you provide a file with extra gamecontroller db entries.
Defined in SDL_hints.h
The file should contain lines of gamecontroller config data, see SDL_gamecontroller.h
This hint must be set before calling SDL_Init(SDL_INIT_GAMECONTROLLER) You can update mappings after the system is initialized with SDL_GameControllerMappingForGUID() and SDL_GameControllerAddMapping()