>> parser.y:25: error: previous declaration of ‘yyleng’ was here
> 

Right; and it's not a makefile problem.  It's a build environment problem.

I recommend pkgsrc.org for getting 3rd party stuff to work on Apples 
these days.  Other projects are mostly in the cut.

~BAS

> Just guessing but it looks like you need yacc / bison or flex
> develpment packages installed (i.e. the .h files and stuff)