Allow ztp-site-generator image to run on arm64 environments

[sebrandon1]

The documentation here mentions running the image:

podman run --log-driver=none --rm registry.redhat.io/openshift4/ztp-site-generate-rhel8:v4.14 extract /home/ztp --tar | tar x -C ./out

This image is incompatible with arm64 environments (such as M-series Mac development machines).

Can we update the image building process to build everything for arm64 as well and push a multi-arch manifest to the image registry?