Respect the required Qt version + some build system improvments
CMAKE_AUTOMOC and CMAKE_INCLUDE_CURRENT_DIR are set by ecm since basically forever, CMAKE_CXX_STANDARD{,_REQUIRED} since ecm >= 5.85.0 and we require 5.89.0 already.
CMAKE_AUTOMOC and CMAKE_INCLUDE_CURRENT_DIR are set by ecm since basically forever, CMAKE_CXX_STANDARD{,_REQUIRED} since ecm >= 5.85.0 and we require 5.89.0 already.