chore(workflows): cache build artifacts

[caugner]

1. Enables sscache using mozilla-actions/sccache-action.
2. Caches Cargo dependencies (via ~/.cargo/registries/{index,cache}/ using actions/cache.

[fiji-flo]

Did you look at https://github.com/mozilla/sccache/blob/main/docs/GHA.md

I think we should either use that or cache the sccache dir.

Also afaik the sccache default location is ~/.cache/sccache.

[caugner]

Did you look at https://github.com/mozilla/sccache/blob/main/docs/GHA.md

I think we should either use that or cache the sccache dir.

Also afaik the sccache default location is ~/.cache/sccache.

Why should we implement/configure the GHA caching ourself or naively cache the whole sccache directory rather than using the dedicated sccache-action that does this for us almost out of the box? It looks like it uses multiple caches, which avoids that the sccache directory grows continuously in size or that you have to recompile everything when the Cargo.lock changes.

I could imagine that the sccache doc regarding GHA is outdated (last edited 9 months ago) and should mention the sccache-action (last commit a few days ago).

[fiji-flo]

Let's get this out.