Update logging section and explain `RUSTC_LOG_COLOR` (#997)
Update logging section and explain `RUSTC_LOG_COLOR` (#997)

* Update logging section and explain `RUSTC_LOG_COLOR`

* Small fixes

Co-authored-by: Léo Lanteri Thauvin <2bf4dd4fd1ac78de2e2ea32757849353d4735b98@gmail.com>

* Mention that prefixes of paths work as log filters

* `=debug` matches `debug!` *and higher*

* Note that `MIRI_LOG_COLOR` only applies to logs from Miri

Co-authored-by: Léo Lanteri Thauvin <2bf4dd4fd1ac78de2e2ea32757849353d4735b98@gmail.com>
rust-lang/rustc-dev-guide,rust-lang/rustc-dev-guide,rust-lang/rustc-dev-guide,rust-lang/rustc-dev-guide