Build dolphin without kdelibs4support

Summary:
Without this change I was not able to build dolphin on MacOS.
I'm not sure if dolphin still needs kdelibs4support but it seems to
build just fine without.

Test Plan: dolphin builds now

Reviewers: vonreth, broulik

Reviewed By: broulik

Subscribers: broulik

Differential Revision: https://phabricator.kde.org/D15244