How can I make a full build for Shield TV 2019 open source

I download source code according nv-tegra.nvidia.com Git - manifest/android/binary.git/blob - README_SHIELD 9, but this one seem is not complete system. How can I make a full build for Shield TV 2019 with latest open source?

I can see the full source code was available till Shield TV 2017 https://nv-tegra.nvidia.com/gitweb/?p=manifest/android/binary.git;a=blob_plain;f=README_NEW_SHIELD;hb=rel-29-partner

But for the higher versions the full source is not available and there is no further clues on how to build the images for a beginner like me.

I too am curious what happened with the recent branches (which are 8 months old as well)

EDIT: additionally the android-toolchain.xml manifest is missing for the toolchain repo