set(BACKEND_SDL_MIXER_X_SRC ${CMAKE_CURRENT_SOURCE_DIR}/sdl_mixer_x.cpp)
set(BACKEND_SDL_MIXER_X_INC ${CMAKE_CURRENT_BINARY_DIR} ${CMAKE_CURRENT_SOURCE_DIR})
add_playback_backend(sdl_mixer_x_backend ${BACKEND_SDL_MIXER_X_SRC})