meson: Add a qt5 feature
This allow opting out items of the builds the depends on QT5 library. Auto-detection of QT5 in cross-build requires host tools to match with the sysroot, and detection of mis-match is not fully reliable.
Due to an influx of spam, we have had to impose restrictions on new accounts. Please see this wiki page for instructions on how to get full permissions. Sorry for the inconvenience.
This allow opting out items of the builds the depends on QT5 library. Auto-detection of QT5 in cross-build requires host tools to match with the sysroot, and detection of mis-match is not fully reliable.