antimass@gem:~$ ls /Library/Frameworks/SDL*
drwxr-xr-x@ 22 Sep 14:54 SDL2.framework
drwxr-xr-x@ 1 Feb 2016 SDL2_ttf.framework
antimass@gem:~$
Wouldn't compile till I added in those SDL frameworks. Note: I also have done 'brew install sdl2' and 'brew install sdl2_ttf' in the past, so maybe you also need those?
brew will install SDL2 in a "unix" fashion, which should work if the makefile is written this way. The Framework version is the "Mac" way that is recognized by Xcode. The makefile for this project was created using the framework version.