how-to-build-and-run.md: fix some text regarding bootstraping

Author: tshepang

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

@@ -231,11 +231,12 @@ probably the best "go to" command for building a local compiler:
 ```
 
 What this command does is build `rustc` using the stage0 compiler and stage0 `std`.
+This produces the stage1 compiler.
 
-To build `rustc` with the in-tree `std`, use this command instead:
+To build the in-tree `std`, use this command instead:
 
 ```console
-./x build rustc --stage 2
+./x build std
 ```
 
 This final product (stage1 compiler + libs built using that compiler)