Fix pri file generation

Summary: The typo probably has been there for quite some time, but only a recent ECM change made it break (D26394)

Reviewers: #kde_pim, mlaurent, vkrause

Reviewed By: #kde_pim, vkrause

Subscribers: kde-pim

Tags: #kde_pim

Differential Revision: https://phabricator.kde.org/D27232