Also auto-generate 24@2x compatibility symlinks

Summary: Missed this in D27557, sorry.

Test Plan:
Delete ~/kde/usr/share/icons/{breeze,breeze-dark} (or wherever your icons live)
Apply patch and build
Look in ~/kde/usr/share/icons/{breeze,breeze-dark}/{devices,actions,places,status}
Notice that @2x symlinks are still there

Reviewers: VDG, ndavis

Reviewed By: VDG, ndavis

Subscribers: kde-frameworks-devel

Tags: Frameworks

Maniphest Tasks: T11950

Differential Revision: https://phabricator.kde.org/D27605