Consider doing an ARM64 build as well

More and more computers are going to arm64, including Macos M1, Windows, single board computers like RaspberryPi 4 etc

The linux arm64 kernel already has support for Macos M1, so it won't be too long before Linux is able to run on that hardware. I would love to see, in the long term, hellosystem running on the M1, but at the moment I would be happy to have a play with hello on the Raspberry Pi 4, oron my Rock64 board.

I have seen the build instructions for the Pi 4, so I could manually do it, but it means a lot of work to upgrade .. how hard is it to add build for arm64 to the build script?