Created attachment 222407 [details]
re-add options LIBXML2
The PR 186890 and following commit http://svnweb.freebsd.org/changeset/ports/347284 made libxml2 non-optional dependency in 2014 for bind99.
The problem mentioned in the PR 186890 is not reproducible for bind916. Time showed the libxml2 library has its own unpleasant backlog of security vulnerabilities. Upstream code of ISC BIND fully supports libxml2 as optional dependency. Let us make it optional dependency again for out port, too keeping it enabled by default to preserve POLA.
Attached patch re-adds option LIBXML2 so one could disable it. PORTREVISION not changed because default built is not affected.