Let ghostscript-encrypt grab its directory directly from aladdin or gnu
ghostscript.
Includes a perfectly sick hack to obtain PDFDIR from those directories:
we do need PORTSDIR at Makefile parsing time, and for that, we just hack
its value from the current Makefile, avoiding endless recursion with
a flag.
Note that this hack is clean though, and doesn't need extra knowledge from
the rest of the ports tree.
f5ef7f193b