Blindly trying to fix the OSX build.

Could need some help here, I lack the hardware to test things. We have
a couple of cmake changes after moving to KDE Frameworks 5. See
https://build.kde.org/job/marble%20master%20stable-kf5-qt5/PLATFORM=OSX,compiler=clang/22/console
Mohammed, are you around? :-)
CCMAIL: nafees.technocool@gmail.com