Add aarch64 wheels to CI

[MichaIng]

Pull Request Checklist

• Pull request is based on the develop branch
• Pull request includes a changelog file. The entry should:
  • Be a short description of your change which makes sense to users. "Fixed a bug that prevented receiving messages from other servers." instead of "Moved X method from EventStore to EventWorkerStore.".
  • Use markdown where necessary, mostly for code blocks.
  • End with either a period (.) or an exclamation mark (!).
  • Start with a capital letter.
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• Pull request includes a sign off
• Code style is correct
  (run the linters)

[DMRobertson]

Closes #13938.

[DMRobertson]

@erikjohnston would you mind taking a look? I think this is sane and I think we're happy to publish arm wheels? Wanted to check though since you mentioned all the extra wheels being painful during the release process.

[DMRobertson]

Run in progress at https://github.com/matrix-org/synapse/actions/runs/3268733324

[erikjohnston]

Yeah, I think this is sane, except for building aarch64 wheels on PRs

[DMRobertson]

Huge thanks for working through this. Are you able to work through the comments we've raised?

[MichaIng]

Are you able to work through the comments we've raised?

Yes will do. Do you prefer commits squashed/amended or separated?

[DMRobertson]

Are you able to work through the comments we've raised?

Yes will do. Do you prefer commits squashed or separated?

Many thanks. Ideally separated on the PR: they'll get squash-merged at the end.

[DMRobertson]

Other than making this not build ARM wheels on PRs I think this is great---thanks again for working through the details.

[DMRobertson]

Thanks again for picking this up when I dropped it!