Fix autotests with -DBUILD_QCH:BOOL=TRUE

Summary:
After 507415c54bd111fbb35716bd9809119d990f9a16 KF5I18nQchTargets.cmake
needs similar adjustments.

Test Plan: The test passes again, KF5I18nQchTargets is still installed

Subscribers: kde-frameworks-devel

Tags: Frameworks

Differential Revision: https://phabricator.kde.org/D15251