1. Adds a regression test to verify #230 ([passing](https://github.com/canonical/craft-archives/actions/runs/33777746941/job/100728034756?pr=255#step:4:50) on arm64 24.04, [failing](https://github.com/canonical/craft-archives/actions/runs/33777746941/job/100728036051?pr=255#step:4:55) on arm64 26.04) 2. For 25.10 and higher, stop adding armhf as a compatible arch for arm64. Instead, users will need to add a `package-repositories` entry for ports.ubuntu.com to get armhf. Originally, I was planning to check if `ubuntu.sources` had a `URIs: ports.ubuntu.com`. This quickly became too complicated. For example, the Github CI runners have `URIs: mirror+file:/etc/apt/apt-mirrors.txt`, and that file contains `azure.archive.ubuntu.com`. Chasing this URL and figuring out if armhf is available there gets complicated. So I opted for a simple check of the Ubuntu base. Fixes #230 Unblocks https://github.com/canonical/snapcraft/issues/6326 (CRAFT-5259) --- - [x] I've followed the [contribution guidelines](https://github.com/canonical/craft-archives/blob/main/CONTRIBUTING.md). - [x] I've signed the [CLA](http://www.ubuntu.com/legal/contributors/). - [ ] I've successfully run `make lint && make test`. - [ ] I've added or updated any relevant documentation. - [ ] In documents I changed, I [added a meta description](https://canonical-starflow.readthedocs-hosted.com/how-to/add-a-page-meta-description/) if one was missing. - [ ] I've updated the relevant release notes.