I also tried the Raspberry Pi Beginners Guide days ago, but with no success.
A more recent Guide is here https://wiki.qt.io/RaspberryPi2EGLFS.
It´s using the offical rpi cross toolchain and a working script to fix the symlink issue.
Also syncing the sysroot from a running image is easier than mounting it with a loop device.
I apologize for necroing an old thread, but this is still a thing in QT 4.2.1. A lot of the time, when I want autocomplete to show, a tooltip telling me what the method I'm currently calling should include pops up instead, sometimes blocking the line above as well so I can't see what I actually want to type. Is there a way to turn this off?