cross compile qtbase5-dev for aarch64 question

[ziyuan <xzy.xu@rock-chips.com>]

hi maintainer,

I have a question for cross compile qtbase5-dev package for debian.

I wanna cross compile aarch64/armhf package for qtbase5-dev, due to the 
GPU of Rockchip SoC can't support OpenGL desktop, they're just support 
OpenGL ES.I have to revert the commit:

commit d35641e169dd5a2db4886f83a1bb558a958e3f68
Author: Lisandro Damián Nicanor Pérez Meyer <perezmeyer@gmail.com>
Date:   Tue Dec 4 13:29:19 2018 -0300

    Revert the arm64 switch to OpenGL ES.

    See <https://lists.debian.org/debian-devel/2018/11/msg00457.html>


As we know, we should use "-xplatform" or "-device" options to configure 
the qtbase5-dev. But I can't find any related 'key word' in 
debian/rules, and I re-build the pakcage use 'dpkg-buildpackage -us -uc 
-B' on sourcecode of qtbase5-dev. I found that all files(*.o) are run 
for amd64 architecture not aarch64.


I tried to 'chroot' a rootfs for aarch64, and use qemu-aarch64 tools to 
cross compile, but it's too slow.

Could you provide any document for cross comiple qtbase5-dev package on 
x64 architecture?

Thanks!

--
Ziyuan Xu