Download the SDL2 binary version (pre-build)
This packages contains the SDL framework for OS X.
Conforming with Apple guidelines, this framework
contains both the SDL runtime component and development header files.
To Install:
Copy the SDL2.framework to /Library/Frameworks
You may alternatively install SDL2.framework in your home directory by creating a subfolder /Library/Frameworks. if your access privileges are not high enough.
Xcode Command Line Tools Installed
https://developer.apple.com/download/more/?=command%20line%20tools