feat: use a manylinux_2_31 compatible image for riscv64

[mayeut]

This ubuntu based image provides better compatibility than the default manylinux_2_39 pypa/manylinux image.

I think it's nice to have this for a base tool like ninja.
Other alternatives:

• the custom ubuntu based manylinux_2_35 image from the same repo which can also be used for cmake (OpenSSL does not build on manylinux_2_31 in the cmake repo but manylinux_2_35 works just fine)
• just close this & keep the default manylinux_2_39 image

[Copilot]

Pull Request Overview

This PR updates the RISC-V 64-bit manylinux image configuration to use a custom Ubuntu-based image that provides better compatibility than the default PyPA manylinux image by downgrading from manylinux_2_39 to manylinux_2_31.

• Replaces the default manylinux_2_39 image with a custom ghcr.io/mayeut/manylinux_2_31:2025.08.02-2 image for RISC-V 64-bit builds

Comments suppressed due to low confidence (1)

pyproject.toml:103

• The image tag references date '2025.08.02-2', but it's currently August 2025. This suggests the image may not exist yet or the date is incorrect.

manylinux-riscv64-image = "ghcr.io/mayeut/manylinux_2_31:2025.08.02-2"

[jcfr]

Do you happen to have a link to the updated Dockerfile ?

(Could not find it looking at https://github.com/mayeut/manylinux/branches)

[mayeut]

Do you happen to have a link to the updated Dockerfile ?

Those images are not part of pypa/manylinux or my fork but are maintained in a different repository: https://github.com/mayeut/manylinux-ubuntu

The python packages come from a ppa (one per distro version, in this case https://launchpad.net/~mayeut-github/+archive/ubuntu/python-focal/+packages) which rebuilds packages from the deadsnakes ppa for all platforms (deadsnakes currently does not build for riscv64).

They get the same tools as pypa/manylinux images & run the same set of tests (using a sub-module on pypa/manylinux).

[jcfr]

Thanks for the thorough answer 🙏 And for maintaining the associated infrastructure 💯