Link directly to the section on --keep-stage

Author: jyn514

src/building/how-to-build-and-run.md

@@ -152,7 +152,9 @@ is what you need to build other Rust programs (unless you use `#![no_std]` or
 
 You will probably find that building the stage1 `std` is a bottleneck for you,
 but fear not, there is a (hacky) workaround...
-see [the section on "recommended workflows"](./suggested.md) below.
+see [the section on "recommended workflows"][keep-stage] below.
+
+[keep-stage]: ./suggested.md#incremental-builds-with---keep-stage
 
 Note that this whole command just gives you a subset of the full `rustc`
 build. The **full** `rustc` build (what you get with `./x.py build