What are the officially supported cross compilers for Ubuntu server alternative architectures like ARM?

I'm interested in the official Ubuntu server ARM image: https://www.ubuntu.com/download/server/arm

How to properly cross compile for it from my x86_64 host?

While a gcc-5-aarch64-linux-gnu C hello world compiled from my 16.04 x86_64 host did work on the 16.04 ARM guest, I don't think it is simple to guarantee that the libc will be binary compatible across Ubuntu versions.

Is it documented anywhere what is the correct cross compiler to use?