Rename rustc_guide to rustc_dev_guide

Author: spastorino

src/doc/rustc/src/contributing.md

@@ -1,12 +1,12 @@
 # Contributing to rustc
 
 We'd love to have your help improving `rustc`! To that end, we've written [a
-whole book][rustc_guide] on its
+whole book][rustc_dev_guide] on its
 internals, how it works, and how to get started working on it. To learn
 more, you'll want to check that out.
 
 If you would like to contribute to _this_ book, you can find its source in the
 rustc source at [src/doc/rustc][rustc_book].
 
-[rustc_guide]: https://rust-lang.github.io/rustc-dev-guide/
+[rustc_dev_guide]: https://rust-lang.github.io/rustc-dev-guide/
 [rustc_book]: https://github.com/rust-lang/rust/tree/master/src/doc/rustc