* Add options to zig compile options
Support for compiling with raygui, raymath, and physac.
Also outputs the required headers.
Raygui should be located `../raygui` relative to the repo root
Physac should be located `../physac` relative to the repo root
This behavior matches options in the Makefile
* Move Options struct
* Remove physac, explicit raymath, always copy rlgl.h and raymath.h
* Remove unused options from build.zig
* Add srcdir as include path for raygui.h
3a90acf08e