`cargo fix` checks packages twice, even if nothing was fixed

[epage]

Problem

Running cargo fix (and worse, cargo clippy --fix on https://github.com/crate-ci/typos is very slow. For clippy, its over 2m.

Proposed Solution

Only re-check the package (to show errors/warnings) if there was output from the first run.

Notes

See also https://rust-lang.zulipchat.com/#narrow/stream/246057-t-cargo/topic/Performance.20of.20.60cargo.20fix.60