Test in AArch64

[coord-e]

Currently tests in AArch46 is entirely disabled:

magicpak/.github/workflows/test.yml

Line 40 in de1e87f

if: matrix.target == 'x86_64-unknown-linux-musl' # TODO: test aarch64

We need to use native ARM builder because we can't ptrace on QEMU.
https://cirrus-ci.org/ might be an option.