sdk_lib: Add description to bash script

Clarify what the bash script does.

BUG=none
TEST=none

Change-Id: Id4aee2a1ae96daa7f1afd58a15bd83a37a0889db
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosutils/+/1967344
Reviewed-by: Will Bradley <wbbradley@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Andrew Lassalle <andrewlassalle@chromium.org>
Tested-by: Andrew Lassalle <andrewlassalle@chromium.org>
Commit-Queue: Andrew Lassalle <andrewlassalle@chromium.org>
diff --git a/sdk_lib/make_chroot.sh b/sdk_lib/make_chroot.sh
index 002e05e..c9370ed 100755
--- a/sdk_lib/make_chroot.sh
+++ b/sdk_lib/make_chroot.sh
@@ -340,7 +340,8 @@
        | user_append "${FLAGS_chroot}/home/${SUDO_USER}/.bash_profile"
 
    # Enable bash completion for build scripts.
-   echo ". ~/trunk/src/scripts/bash_completion" \
+   printf '%s\n' "# Set up bash autocompletion." \
+        ". ~/trunk/src/scripts/bash_completion" \
        | user_append "${FLAGS_chroot}/home/${SUDO_USER}/.bashrc"
 
    if [[ -f "${SUDO_HOME}/.cros_chroot_init" ]]; then