Add example

Author: JonathanBrouwer

src/tests/compiletest.md

@@ -203,8 +203,10 @@ The attribute takes the following arguments:
   This can be useful to ensure that a test is actually exercising the deserialization
   logic for a particular query result. This can be combined with `except`.
 
-[`tests/incremental`]: https://github.com/rust-lang/rust/tree/HEAD/tests/incremental
+A simple example of a test using `rustc_clean` is the [hello_world test](#helloworld).
 
+[`tests/incremental`]: https://github.com/rust-lang/rust/tree/HEAD/tests/incremental
+[`helloworld`]: https://github.com/rust-lang/rust/tree/HEAD/tests/incremental/hello_world.rs
 
 ### Debuginfo tests