Makefile Help?

Hi all, I'm trying to understand the build process for PHP-Gtk2 and why generator/generator.php doesn't generate the gen_*.c and gen_*.h files under FreeBSD. I can see where generator/generator.php is called in the toplevel Makefile. At some point before this in the Makefile, the operating system must be identified, right? What I'm trying to figure out is which shell script _originally_ identifies the OS. Why: Near the top of config.log, the message, "checking for Cygwin environment" suggests to me (correct me if I'm wrong) that the OS is being mis-identified as Windows. Is the OS identified by examining an environment variable or in some other way? Any help on this will be very much appreciated. -Ron T.