Pin Rust to 1.81.0

[unexge]

• Create rust-toolchain.toml
• Use actions-rust-lang/setup-rust-toolchain GitHub action as it supports rust-toolchain.toml

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[passaro]

@unexge, is the rust-toolchain action actually required? My understanding is that cargo will respect rust-toolchain.toml automatically.

[unexge]

@passaro, not sure. It's a popular request for dtolnay/rust-toolchain to support rust-toolchain file, so I assumed it won't work. But let me give it a try.

[passaro]

My suggestion was to remove this step entirely, not to revert to stable

[passaro]

Alternative: we could look at some other actions, e.g. https://github.com/marketplace/actions/rust-toolchain-toml-install

[unexge]

Agh, I misunderstood. I think dtolnay/rust-toolchain installs rustup/cargo. We might look installing it in .github/actions/install-dependencies step, not sure if there are any downsides.

[dannycjones]

I was wondering about jumping to a new action, I saw this one that looks well maintained: https://github.com/actions-rust-lang/setup-rust-toolchain

[unexge]

Updated to use actions-rust-lang/setup-rust-toolchain. I had to override rustflags option though, it's -D warnings by default which turns all warnings into compile errors, and vendor/fuser has lots of warnings. It'd be nice to get rid of those warnings eventually, but not turning this on should be fine for now.

This new action also surfaces warnings on PRs, e.g., scroll to the bottom on https://github.com/awslabs/mountpoint-s3/pull/1073/files. We can turn this of it we find it noisy, but eventually I'd like to address these warnings as well.