@mitu

You should add arm_64bit=0 to config.txt and reboot
Try adding PTR64=0 to the build options

That were the solutions.
I expect it will also work without using PTR64=0 now.
Compiling seems to be about 10 hours on a RPI4/8GB which is much better than 1 month on a PI0/1.

So now I have a working binary and channelf is working as expected ;-)
Will try some other systems later.

Thanks !

A lot of this functionality is built in

eg. on your ubuntu machine

sudo ./retropie_packages.sh crosscomp setup stretch

then on the rpi3 just install distcc, configure it to use Ubuntu machine.

for building:

PATH="/usr/lib/distcc:$PATH" MAKEFLAGS="-j4 PATH=/usr/lib/distcc:$PATH" ./retropie_packages.sh etc

note settings the PATH for makeflags is needed for some modules to use distcc.

retropie also includes the facility to build raspberry pi binaries on an x86 Ubuntu machine using an emulated chroot and the distcc on the host. see the "builder" module.