Fixes two minor issues with the multi-arch support

[dmikusa]

Summary

1. Bellsoft calls the arch arm, but they strip off the bitness for their own reasons. We are not going to do that cause most places want arm64 not just arm. Thus, we look for arm64 and convert it to just arm for Bellsoft's api.
2. Pass the arch into the update-buildpack-dependency tool. It now uses it to select what is updated.

Use Cases

Multi-arch support.

Checklist

• I have viewed, signed, and submitted the Contributor License Agreement.
• I have linked issue(s) that this PR should close using keywords or the Github UI (See docs)
• I have added an integration test, if necessary.
• I have reviewed the styleguide for guidance on my code quality.
• I'm happy with the commit history on this PR (I have rebased/squashed as needed).