Add build requirements, steps and commands from the command line.
Also, restructure the sections into an easier flow to follow.

Pick-to: 3.0
Change-Id: I8fd58246d555aa215e5a2ed9acc4994c22cbe8b3
Reviewed-by: Nikunj Arora <nikunj.arora@qt.io>
Reviewed-by: Tinja Paavoseppä <tinja.paavoseppa@qt.io>