ci: couple of potential improvements
While porting zbus's ci to fdo template I experimented with a couple of changes:
Installing Rust stable and nightly on the same image, using
rustup override set $xin each job to pick the version we want. This would help simplifying our ci setup as we'd have only one image instead of 3 (4 including the base one).
cargo fetchwhen generating the image so build deps are part of the image, saving each job to re-download them. Only worth if images are refreshed frequently enough that those deps stay relevant. Shouldn't be a problem if we regenerate the image each week for nightly I think.
We can wait a bit to see how it works for
zbus and then consider doing the same for our ci here.