[OSuser]SDL2库

$apt-cache search libsdl2
- libsdl2-dev
- libsdl2-image-dev
- libsdl2-ttf-dev
若没有以上lib，则
$sudo apt-get install libsdl2

若出现usr/include/里面没有SDL库，则：
$sudo apt-get install libsdl2-dev
$sudo apt-get install libsdl2-image-dev
$sudo apt-get install libsdl2-ttf-dev