Provide sandbox.o for other architectures

[KyeRussell]

Is your feature request related to a problem? Please describe.
I cannot use sandbox.o in non-x86-64 environments, e.g. More concretely/specifically, I can't run Packj on an Apple Silicon (ARM) Mac without using some sort of emulation/translation/virtualisation layer (e.g. running the amd64 Docker image).

Describe the solution you'd like
Ideally, sandbox.o should be open-sourced, but I can see that this has been discussed elsewhere (e.g. #67). In which case, a compilation should be provided for other common architectures (like ARM).