Use stable toolchain as default for ink! related CI images

[HCastano]

After use-ink/cargo-contract#698 we're able to build contracts
using the stable toolchain instead of nightly.

This updates our CI images to use stable as the default toolchain.

[athei]

Won't this break the ink! CI? Building ink! itself (when not done by cargo contract) still needs nightly or RUSTC_BOOSTRAP=1.

[HCastano]

You're right, I got too excited 😆 This change could still work but we'd need to manually set +nightly to the places where we build ink! for Wasm. Tomorrow problem though, haha (so don't merge pls)

[athei]

This change could still work but we'd need to manually set +nightly to the places where we build ink! for Wasm.

I would say merge this but change the ink! CI to put RUSTC_BOOTSTRAP=1 into the environment. Cause we should build on stable in our CI when we expect the same thing from our users.

[HCastano]

I would say merge this but change the ink! CI to put RUSTC_BOOTSTRAP=1 into the environment. Cause we should build on stable in our CI when we expect the same thing from our users.

Okay that makes sense. We can also use RUSTC_BOOTSTRAP=1 when doing our Clippy-Wasm checks which should save us some headaches ¹. We will still need to use +nightly when running cargo fmt since we're using some config settings which they consider unstable.

Footnotes

1. I've thought about this a bit and I'm not sure we want to do this, since contributors to ink! will have to use RUSTC_BOOTSTRAP=1 locally to check that Clippy passes. I'd prefer if they were told to use nightly instead. ↩

[athei]

You could still tell developers to use nightly for local development. But the CI should use stable cause that is what we are delivering to our users.