A lot of works has already been done at
I'm thinking of putting the additional sections into the public wiki for now, rather than the official docs, for a faster turnaround.
Document difference between configure args and CMake args, how to mix them and the pass them to configure.
Provide sample configuration options for each main platform at https://wiki.qt.io/Building_Qt_6_from_Git, or at least link to the docs in https://doc.qt.io/qt-6/build-sources.html e.g. specifics for MinGW, Android, iOS.
Document the various ways to build and configuring Qt tests: in-tree tests, standalone-tests, qt-cmake-standalone-test