./configure 编译安装 graphic 库的时候报错
*** The sdl-config script installed by SDL could not be found
*** If SDL was installed in PREFIX, make sure PREFIX/bin is in
*** your path, or set the SDL_CONFIG environment variable to the
*** full path to sdl-config.
configure: error: *** SDL version 1.2.0 not found!
sdl 是啥啊