D10603: Make DMTX dependency optional

[Sune Vuorela]

svuorela accepted this revision.
This revision is now accepted and ready to land.

REPOSITORY
  R280 Prison

BRANCH
  master

REVISION DETAIL
  https://phabricator.kde.org/D10603

To: vkrause, #frameworks, svuorela
Cc: michaelh