Arm64 support in dockerfile.merlin

[jlinford]

Resolves #834 to add support for Arm64 in the Merlin base image. Additional changes are needed in other dockerfiles to broadly enable Arm64 support, but this is a start.

[jlinford]

I've successfully built on both arm64 and amd64 via docker build - < docker/dockerfile.merlin.

[github-actions]

Documentation preview

https://nvidia-merlin.github.io/Merlin/review/pr-846

[karlhigley]

This LGTM but I want to get eyes on it from the people working on our container releases before pushing the big green button 😄

[jperez999]

@jlinford does the build command have to change for all builds? Like to build the non-arm docker image do I need to use docker build - < docker/dockerfile.merlin or does docker build -t <tag name> -f docker/dockerfile.merlin . ? If so, because we are in release right now I am going to hold off until that is complete before adding this because we will need to change CI commands in the container build process.

[jlinford]

The build command should not change, either on arm64 or x86_64. On arm64, it should be possible to use the exact same build command you currently use on x86_64, and get an arm64 image as a result. If that doesn't work, I'd consider it a bug and would want to fix it.

[jlinford]

Apologies, I think I accidentally removed @oliverholworthy and @edknv from the reviewers, but somehow can't add them back. Happy to have their review!

[jperez999]

I approved... but we will wait to merge. Sorry I should have done that when we resolved the comments.