Akonadi: add missing dependencies on included XSL files
Summary:
Editing e.g. src/server/storage/entities-source.xsl
didn't lead to entities.cpp being regenerated.
Test Plan: make now rebuilds entities.cpp
Reviewers: dvratil, vkrause
Reviewed By: vkrause
Subscribers: kde-pim
Tags: KDE PIM
Differential Revision: https://phabricator.kde.org/D18887