A few months ago, sdocbook-xml was split up along with many other
docbook ports to use a common makefile. Since then, the other docbook
ports have been consolidated into two flavors (xml and sgml) and neither
use the textproc/docbook/bsd.docbook.mk makefile.
Moreover, it conditionally sets the EXTRACT_SUFX to .zip, but without
setting USES+= zip which is now required for all zip distfiles.
The cleanest fix is to move the needed bits from the common makefile
back into sdocbook-xml and delete the common makefile. It passed 8x
on redport and DragonFly (w/ AK archiver patch in place)
Approved by: portmgr (mat)
3067d29901