The `eek/layersurface.c` file should be excluded because it's an imported, "foreign" source, but clang-tidy doesn't seem to have an annotation for that.

An alternative would have been to exclude it in Meson and do the check there, but that requires clang-tidy, raising the barrier to contribute of Squeekboard even more (it already requires libfeedback, which isn't packaged widely).

This makes sure we don't have more warnings creeping in

This commit is a bit bigger than it could have: Meson changes could have gone in separately from CI and Debian.

This commit looks more complicated than it should reasonably be. Alas, Cargo is a piece of work, and it doesn't let honest people just choose different versions of dependencies, leading to a cascade of misery. Several things were tried to curb the disaster:

- Cargo [feature] supports choosing dependencies, but doesn't support specifying dependency versions
- Cargo has a cfg() syntax in sections for choosing dependencies by build options, but it explicitly doesn't support selecting on features…
- Cargo allows choosing different dependencies based on features, so perhaps dependencies with different versions could live in stub crates pulled in as needed? Nope! If a dependency doesn't exist in the repo (and that's the point here), Cargo throws up its hands.

This means Cargo.toml needs to be generated based on the build type. More misery:

- we lose the simplicity of just doing `cargo.sh` for simple housekeeping like deps updates. HACKING.md was updated to reflect that. Perhaps that's inevitable - build options need to be like this.
- Some flaky adjustments needed in `cargo.sh` because of an additional argument that can be mistaken for an argument to the exec in `cargo run`.
- Specifying a custom `Cargo.toml` means Cargo can no longer find any tests, examples, benchmarks, or binaries, because it searches relative to the directory of `Cargo.toml`, which is now the build dir. Extra care needed to not forget about them now.

As soon as Cargo allows anything better for managing deps versions, the above should be undone in its favor.

Good side is that a couple bugs went away:

- build flags not always making it to Cargo
- arm64 builds were optional while they shouldn't
- test layouts in unit tests are loaded from an explicit directory now

The Bullseye versions of dependencies are canonical now, Buster considered legacy.

Prevents forgetting to sign the tag, which is currently done out of band and independently of review.

GitLab doesn't always clean up the `..` directory, leaving things that are lated picked up as artifacts. The new rule cleans up anything that looks like an artifact before fresh ones are generated.

Create docs, based on Sphinx with Commonmark, seeding it with https://forums.puri.sm/t/translations-and-virtual-touch-keyboards-tracking-localization/7669/48?u=dcz

There's no need to keep it for a long time, as its only purpose is to feed the test stage

Pros: Ability to use Rust libraries from crates.io
Problems: Need to lock library versions and document their reproducible building, either via Cargo.lock or vendoring.

We create widgets so need a display.

Just using debian buster makes things more stable.

Following comments on Librem5/squeekboard!20

Instead, require virtboard to provide it.

This commit includes a little restructuring necessary for keeping wayland objects properly.
It doesn't fix broken modifier functionality yet.

This breaks autoconf. The only resulting binary is the squeekboard GUI. It still needs the autotools-built eekboard client in order to do anything useful. That one needs to be built using a different branch, making this a WIP.