FindQHelpGenerator: try to find Qt5Help instead of Qt5Core
Summary:
The Qt5Help CMake modules contain the Qt5::qhelpgenerator target, so
look for that instead of Qt5Core. Otherwise, the Qt5::qhelpgenerator
is available only if Qt5Help was searched previously (which does not
happen often).
Using the Qt5::qhelpgenerator is more reliable than the search for the
qhelpgenerator executable based on the qmake path.
Test Plan:
build some framework with -DBUILD_QCH=ON, and notice that
the right path of qhelpgenerator is found directly with the
Qt5::qhelpgenerator target.
Reviewers: kossebau
Reviewed By: kossebau
Subscribers: kde-frameworks-devel, kde-buildsystem
Tags: Frameworks, Build System
Differential Revision: https://phabricator.kde.org/D16938