establish installed dependency not in portfile

[db]

On 9 Oct 2017, at 16:00, Rainer Müller <raimue at macports.org> wrote:
> On 2017-10-09 15:21, db wrote:
>> There are still no binaries for all ports for the previous supported OS releases, i.e., 10.11 and 10.12.
> Due to license conflicts, we cannot distribute binaries for all ports.

I rather thought that the buildbots didn't finished all binaries for those OS versions yet.