Fixes build issues on Linux and Mac so hopefully can build against Raylib 3.7 or Raylib 4.0.
Fixes build issues on Windows by hardcoding a path :-(
4.0a6
* Adds rlgl. * Makes raygui and physac optional depending on whether it finds the headers when compiling. * Header processing (on Unix at least) is now entirely automated, so should work with all future versions of Raylib with no changes (yeah right).