This is needed because commit 0be57eec6e
changed the location of the nimbus_beacon_node executable within the
container file system. For users, not relying on the official entrypoint
this was a breaking change.
We're moving from very slow QEMU-virtualised builds to very fast ones
based on cross toolchains.
- refactor jobs; add checksums to release note
- build and publish Docker images with ARM/ARM64 binaries