D18674: Add missing QStandardPaths to fix build

[Yuri Chornoivan]

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

REPOSITORY
  R181 Amarok

BRANCH
  buildfix

REVISION DETAIL
  https://phabricator.kde.org/D18674

To: asturmlechner, #amarok, markey, yurchor
Cc: yurchor, amarok-devel