Fix "Potential incomplete link" error on compiler-debugging.md

Author: JohnTitor

src/compiler-debugging.md

@@ -182,11 +182,13 @@ If you are developing rustdoc, use `RUSTDOC_LOG` instead. If you are developing
 Miri, use `MIRI_LOG` instead. You get the idea :)
 
 See the [`tracing`] crate's docs, and specifically the docs for [`debug!`] to
-see the full syntax you can use. See the [env-logger] doc for more info on the
+see the full syntax you can use. See the [`env_logger`] doc for more info on the
 full syntax. (Note: unlike the compiler, the [`tracing`] crate and its examples
 use the `RUST_LOG` environment variable. rustc, rustdoc, and other tools set
 custom environment variables.)
 
+[`env_logger`]: https://docs.rs/env_logger
+
 **Note that unless you use a very strict filter, the logger will emit a lot of
 output, so use the most specific module(s) you can (comma-separated if
 multiple)**. It's typically a good idea to pipe standard error to a file and