I have a problem with cross-compiling netifaces extension under Buildroot Linux distro for ARM (Python 2.7.2). According to this blog http://whatschrisdoing.com/blog/2009/10
Make sure you have installed the distutilscross package as noted in the article you linked. This adds the -x option and support for PYTHONXCPREFIX/LDSHARED/etc environment variables.
I don't know whether you still care this question. It seems that you have some build target already, so it doesn't compile the c program any more. Try to clean all the files and directories below "build" folder, and build again.