build_packages: Add log message to help debug crbug.com/849414

TEST=none
BUG=chromium:849414

Change-Id: I6a244aacfdf6732c8964550434fcc9118c303643
Reviewed-on: https://chromium-review.googlesource.com/1087829
Commit-Ready: Jason Clinton <jclinton@chromium.org>
Tested-by: Jason Clinton <jclinton@chromium.org>
Reviewed-by: Lann Martin <lannm@chromium.org>
diff --git a/build_packages b/build_packages
index e194a5e..434bd30 100755
--- a/build_packages
+++ b/build_packages
@@ -313,6 +313,7 @@
     || die "${FLAGS_save_install_plan} does not exist"
   readarray NEW_DEPS < ${FLAGS_save_install_plan}
   if [[ ${#NEW_DEPS[@]} -gt 0 ]]; then
+    echo "Found new deps: '${NEW_DEPS[*]}'. Converting deps to package names."
     # Convert specific versions into base package names
     MOD_PKGS+=( $(\
       equery-${FLAGS_board} list -p -o --format='$category/$name' \