Fix verify-generated-files to error on untracked files

hack/verify-generated-files.sh

@@ -39,11 +39,11 @@ git clean -ffxd
 # regenerate any generated code
 make generated_files
 
-diff=$(git diff --name-only)
+changed_files=$(git status --porcelain)
 
-if [[ -n "${diff}" ]]; then
+if [[ -n "${changed_files}" ]]; then
   echo "!!! Generated code is out of date:" >&2
-  echo "${diff}" >&2
+  echo "${changed_files}" >&2
   echo >&2
   echo "Please run make generated_files." >&2
   exit 1