Okay, buildling a builtin.mk seems simple enough, but how would I go 
about specifying the additional library that is required to link with 
libfam on IRIX?

And now for something completely different...
I also just remembered that gimp2 wouldn't configure with the built-in
awk because of too long input lines (I did bmake AWK=/usr/pkg/bin/gawk)
and more serious, some rpaths got mangled by the new wrappers, colons
disappeared so I ended up with paths like
/usr/pkgsrc/foo/bar/work/.buildlink/lib/usr/pkgsrc/foo/bar/work/bar-1.0/.lib.
Gtk2 did this that I noticed, since it needs to run some program linked
with the not-yet-installed libgtk-2.0

Regards,

-- 
Staffan Thomen
1024D/7C7E2EF8