If you have installed freetype on OS X via HomeBrew, it installs freetype2. This package is installed at: /opt/X11/include/freetype2

A lot of other packages depend on freetype and look for it at: opt/X11/include/freetype
on not finding the said location, throw an error: freetype/freetype.h: No such file or directory

The solution is simple.

$ cd /opt/X11/include/
$ ln -s freetype2/ freetype