Hola,
I have created a PKGBUILD on AUR which should simplify the cross compilation of Qt for the Raspberry PI 2. My goal is to get it to a point where you simply need to:
yaourt -S qpii
on a host machine with a pi mounted, and you should be golden.
It should already be functional with the following provisos:
1) The host/target tools are currently all deployed to the sysroot (qmake for your Arch build host is actually installed to the Pi itself)
2) You need to install some deps that are documented in the PKGBUILD (basically, install the chromium browser and you should get everything you need)
I am hoping this is of use to someone since cross compiling Qt is way more effort than it should be, and Qt is awfully functional of a Raspberry pi, even as of right now. Let me know if you want to help or if this is of use to you.
Yours sincerely,
Donald Carr