First attempt to build qt5-qt-webengine on arm64

[adr <adr%SDF.ORG@localhost>]

Hi,

The first problem I found is that
src/3rdparty/chromium/base/system/sys_info_posix.cc is using uname(3)
to use the machine member in the utsname structure to get the cpu
architecture. I'm curious, why isn't a machine_arch member in that
structure? NetBSD use of evbarm for both arm and aarch64 make this
situation problematic. Is there other packages using uname(3) that
have been patched that you could recommend me as a common practice
os should I just add a conditional block and use sysctl(3)?

Regards,
adr.