Recover caveat about -vv and cleaning

First added in 72c924230c3df67261642f74ba415cb34086935f 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 aa62140b8612d553269bb3d49f24e653110b9245..53074238c217791b79ff67764568ad3f7414b33a 100644 (file)
--- a/src/doc/src/reference/build-scripts.md
+++ b/src/doc/src/reference/build-scripts.md
@@ -48,9 +48,13 @@ 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). 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:
+invoke cargo as 'very verbose' with the `-vv` flag. Note that if neither the
+build script nor project source files are modified, subsequent calls to
+cargo with `-vv` will **not** print output to the terminal because a
+new build is not executed. Run `cargo clean` before each cargo invocation
+if you want to ensure that output is always displayed on your terminal.
+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