Add support for building aarch64 wheels

[bennuttall]

In order to build aarch64 wheels, we need to add the logic for separating armv6/armv7 and aarch64, and enable ABIs per architecture, i.e. armv6/armv7: cp34m, cp35m, cp37m; aarch64: cp37m.

We'll also need to set up another set of aarch64/cp37m builders and rebuild all the non-pure-python packages.

[bennuttall]

Current state of piwheels builders:

• Jessie armv7 (symlink to armv6)
• Stretch armv7 (symlink to armv6)
• Buster armv7 (symlink to armv6)

Since Jessie is approaching EOL, we can drop that, but we'll need to add aarch64, which is Buster only, so we'll have the following builders:

• Stretch armv7 (symlink to armv6)
• Buster armv7 (symlink to armv6)
• Buster aaarch64

And once Bullseye is out next summer:

• Stretch armv7 (symlink to armv6)
• Buster armv7 (symlink to armv6)
• Buster aaarch64
• Bullseye armv7 (symlink to armv6)
• Bullseye aarch64

This also relies on Mythic having a 64-bit OS

[carlosperate]

In the meantime, can't aarch64 symlink to armv7/6? Shouldn't the wheels from those platforms work in aarch64?

[bennuttall]

No, they're not compatible.

[rkhaled0]

👋 everyone, any updates ?

[bennuttall]

Not yet

[leigh-johnson]

Hey @bennuttall, thank you so much for all the work you've done on PiWheels! I'm wondering if you're looking for help with this?

A bit of background: I build armhf/aarch64 wheels for scientific computing and ML/deep learning.

I just picked up one of these to run as a CI/CD matrix, and I'd be interested in running my own PiWheels instance. Happy to contribute to this work.

[bennuttall]

Instructions for setting up your own piwheels instance are provided in the docs: https://piwheels.readthedocs.io/en/latest/

To modify it so it only builds aarch64 wheels should be fairly trivial. To modify it to queue up builds correctly for armv6/7 and aarch64 is more complex.

Give it a try and let us know if you have any issues you can't get past. Probably best by email - ben [at] bennuttall.com

[bsimmo]

How's this going