>From the investigations I've done it seems it is looking for a header file
  that is part of glib2, which is installed. I can find the header file glib.h
  in /usr/include/glib/glib2.0/

Usually this means that your glib installation is old, or broken, or
is out of sync with the buildlink3 file.   When I have had these
problems, rebuilding glib (usually gtk actually) has solved them.

Or, you can manually fix up the symlinks to put the includes and
perhaps libs into your work/.buildlink directory.

-- 
        Greg Troxel <gdt@ir.bbn.com>