D15795: Fix warnings about deprecated install dirs

[Dino H.]

dinoh added reviewers: apol, bruns, dfaure.

REPOSITORY
  R240 Extra CMake Modules

REVISION DETAIL
  https://phabricator.kde.org/D15795

To: dinoh, apol, bruns, dfaure
Cc: kde-frameworks-devel, kde-buildsystem, michaelh, ngraham, bruns