Fix reference

Co-Authored-By: Who? Me?! <mark-i-m@users.noreply.github.com>

Author: georgewfraser

src/rustc-driver.md

@@ -37,7 +37,7 @@ replaces this functionality.
 [cb]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_driver/trait.Callbacks.html
 [rd_rc]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_driver/fn.run_compiler.html
 [i_rc]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_interface/interface/fn.run_compiler.html
-[example]: https://github.com/rust-lang/rustc-dev-guide/blob/master/src/rustc-driver-example.rs
+[example]: https://github.com/rust-lang/rustc-dev-guide/blob/master/examples/rustc-driver-example.rs
 [`rustc_interface`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_interface/index.html
 [`rustc_driver`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_driver/
 [`Compiler`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_interface/interface/struct.Compiler.html