Custom build strategy cannot add configmaps as build input

If we add a configmap to buildconfig as build input, the configmap data is not present at the destnationDir on the build pod.

Follow below steps to reproduce.

1. Create a configmap to pass as build input

apiVersion: v1
data:
  settings.xml: |+
    xxx
    yyy
kind: ConfigMap
metadata:
  name: build-test
  namespace: test

2. Create a buidlconfig like below

apiVersion: build.openshift.io/v1
kind: BuildConfig
metadata:
  labels:
    app: custom-build
  name: custom-build
spec:
  source:
    configMaps:
    - configMap:
        name: build-test
      destinationDir: /tmp
    type: None
  output:
    to:
      kind: ImageStreamTag
      name: custom-build:latest
  postCommit: {}
  runPolicy: Serial
  strategy:
    customStrategy:
      from:
        kind: "DockerImage"
        name: "registry.redhat.io/rhel8/s2i-base"

 3. start a new build

    oc start-build custom-build

 4. As per the documentation[a] the configmap data should present on the build pod location "/var/run/secrets/openshift.io/build" if we didn't explicitly mention the "destinationDir". in above example "destinationDir" set to "/tmp" so "server.xml" file from the configmap should present in "/tmp" directory of the build pod.
 
[a] https://docs.openshift.com/container-platform/4.12/cicd/builds/creating-build-inputs.html#builds-custom-strategy_creating-build-inputs

Configmap data is not present on the "destinationDir" or in default location "/var/run/secrets/openshift.io/build"

Configmap data should be present on the destinationDir of the builder pod.