Let Cargo track CLIPPY_ARGS
This PR makes `clippy-driver` emit `CLIPPY_ARGS` in its `dep-info` output.
Just like #6441, this allows this workflow to work:
```shell
cargo clippy # warning: empty `loop {}` wastes CPU cycles
cargo clippy -- -A clippy::empty_loop # no warnings emitted
```
But without rebuilding all dependencies.
cc https://rust-lang.zulipchat.com/#narrow/stream/257328-clippy/topic/CLIPPY_ARGS.20is.20not.20tracked.20by.20Cargo/near/228599088
changelog: Cargo now re-runs Clippy if arguments after `--` provided to `cargo clippy` are changed.
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