This macro should help with setting up all the boilerplate CMake code needed
to instruct automoc about the custom C++ macros used to define Qt-style
plugin class instances.
Open questions:
A) names of macro and arguments okay?
B) other/similar/related use cases which should be covered?
C) how to design argument passing for all the arg1, arg2, arg3? Is the currrent approach sane or how to support someone needing some arg5?
This new macro targets ECM 5.45 in April, ideally committed right after
5.44 being tagged.
See also:
* intermediate non-ecm-macro-based fixes for KF5 modules by D10733, D10732, D10724
* related CMake issue https://gitlab.kitware.com/cmake/cmake/issues/17750