Generate for staging directories that are not client-go

hack/make-rules/helpers/cache_go_dirs.sh

@@ -36,7 +36,11 @@ trap "rm -f '${CACHE}'" HUP INT TERM ERR
 # Example:
 #   kfind -type f -name foobar.go
 function kfind() {
-    find .                         \
+    # include the "special" vendor directories which are actually part
+    # of the Kubernetes source tree - generators will use these for
+    # including certain core API concepts.
+    find -H . ./vendor/k8s.io/apimachinery ./vendor/k8s.io/apiserver \
+        \(                         \
         -not \(                    \
             \(                     \
                 -path ./vendor -o  \
@@ -47,6 +51,7 @@ function kfind() {
                 -path ./examples   \
             \) -prune              \
         \)                         \
+        \)                         \
         "$@"
 }