Matching GHA for ubuntu-latest (ubuntu-26.04-riscv) #142

GHA's ubuntu-latest tag is in the process of migrating to Ubuntu 26.04 by default, with a planned completion date of November 19th, 2026. See actions/runner-images#14748. After that point, projects using the runners for riscv64 builds may find that they have to add extra workarounds and/or separate build steps/jobs to accommodate the architecture, which could make upstream submissions more challenging.

Should we get the ubuntu-26.04-riscv label ready, and start using it in workflows? The docs page still shows it as early access.