Fix path of Mainpage.dox passed to ecm_add_qch()
It has been moved in [1] without adjusting the path, which is passed to ecm_add_qch(). Fixes the build with -DBUILD_QCH:BOOL=TRUE.
[1] 7ae9af91
It has been moved in [1] without adjusting the path, which is passed to ecm_add_qch(). Fixes the build with -DBUILD_QCH:BOOL=TRUE.
[1] 7ae9af91