kustomize: Namespace generated is missing document separator

When stacking multiple kustomize outputs together it becomes apparent that the emitted namespace is missing the ---.

Also, when a namespace is included and added to resources, it has the document separator removed.

This is preventing doing e.g.

for i in *
do
kustomize build $i
done | kubectl apply -f -

$ kustomize build .
apiVersion: v1
kind: Namespace
metadata:
  name: x
---
apiVersion: v1
data:
  druid_segmentCache_locations: '[{"path": "var/druid/segment-cache", "maxSize": 32000000000,
    "freeSpacePercent": 1.0, "blahblahblah":"9999999999"}]'
kind: ConfigMap
metadata:
  name: foo-b66gf6d7t6
  namespace: X
$ cat kustomization.yaml 
namespace: X

resources:
  - namespace.yaml

configMapGenerator:
  - name: foo
    literals:
      - 'druid_segmentCache_locations=[{"path": "var/druid/segment-cache", "maxSize": 32000000000, "freeSpacePercent": 1.0, "blahblahblah":"9999999999"}]'
don@cube[gke-noctest]:y
$ cat namespace.yaml 
---
apiVersion: v1
kind: Namespace
metadata:
  name: x