Now I just tried a fresh Deian buster and I am still getting the same issue, I followed all the steps in the build documentation and still came up with the empty ISO, not sure if I am missing something?
Thanks @blason - I can now build the iso using the latest docs.
One other question I could not tell which version was built the only number it was showing is vyos-999.202106270838-amd64.iso
show version was giving the same output. I know there is version flag in the ./configure script but how can I know the latest releases for a particular version (like the 1.2.x)?