Recover discussion of -vv for build output

First added in 723945cb0eae7d642caa88812c6ecee3ed5895a1 which failed
to update the book and was replaced in
1271bb4de0c0e0a085be239c2418af9c673ffc87.

diff --git a/src/doc/src/reference/build-scripts.md b/src/doc/src/reference/build-scripts.md
index a50f3afea159860165f472bb14f8d8af55aef1a7..42113a1ffe21e911108ddeb1fb2aa87b2fe623d0 100644 (file)
--- a/src/doc/src/reference/build-scripts.md
+++ b/src/doc/src/reference/build-scripts.md
@@ -47,8 +47,10 @@ the source directory of the build script’s package.
 
 All the lines printed to stdout by a build script are written to a file like
 `target/debug/build/<pkg>/output` (the precise location may depend on your
-configuration). Any line that starts with `cargo:` is interpreted directly by
-Cargo. This line must be of the form `cargo:key=value`, like the examples below:
+configuration). If you would like to see such output directly in your terminal,
+invoke cargo as 'very verbose' with the `-vv` flag. Any line that starts with
+`cargo:` is interpreted directly by Cargo. This line must be of the form
+`cargo:key=value`, like the examples below:
 
 ```shell
 # specially recognized by Cargo