D12674: Mark `Phonon4Qt5` dependency as optional in CMakeLists file

[Alexander Schlarb]

tundracomp updated this revision to Diff 33575.

CHANGES SINCE LAST UPDATE
  https://phabricator.kde.org/D12674?vs=33526&id=33575

REVISION DETAIL
  https://phabricator.kde.org/D12674

AFFECTED FILES
  CMakeLists.txt

To: tundracomp
Cc: ltoscano, cgiboudeaux, #frameworks, michaelh, bruns