The rcc compiler should output a list of files that it depends on to make integrating it to build systems easier.
A simple use case is putting qml files in qresources and triggering a rebuild when the qml files are changed. This is described in detail here: https://github.com/jpakkane/meson/issues/97
Having rcc produce this dependency file is the most user-friendly approach, because then it will always be up to date and the user don't need to write the list of files in two places (the qrc and the build definition file).
There is a similar bug report for Gnome's resource compiler here: https://bugzilla.gnome.org/show_bug.cgi?id=745754