D9056: Add the description tag to the generated pkgconfig files

[David Faure]

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

REPOSITORY
  R240 Extra CMake Modules

BRANCH
  pkgconfig-part1

REVISION DETAIL
  https://phabricator.kde.org/D9056

To: cgiboudeaux, dfaure, apol
Cc: #frameworks, #build_system