BuildConfig inline Dockerfile fails with heredoc syntax

4.17, 4.18, 4.19

    Always

 1. Apply the following resources:
```
apiVersion: image.openshift.io/v1
kind: ImageStream
metadata:
  labels:
    ad-hoc: build-inline-dockerfile-heredoc
  name: foo
---
apiVersion: build.openshift.io/v1
kind: BuildConfig
metadata:
  labels:
    ad-hoc: build-inline-dockerfile-heredoc
  name: foo
spec:
  output:
    to:
      kind: ImageStreamTag
      name: foo:latest
  resources:
    requests:
      cpu: .5
      memory: 10Mi
    limits:
      cpu: 1
      memory: 100Mi
  source:      
    dockerfile: |
      FROM registry.access.redhat.com/ubi9/ubi:latest
      COPY --chmod=+x <<EOF /entrypoint.sh
      #!/bin/bash
      printf "hello world!"
      EOF
      ENTRYPOINT ["/entrypoint.sh"]   strategy:
    type: Docker
```

2. Start the build:
```
$ oc start-build foo --follow
```

Build fails with:
error: EOF: unterminated heredoc

The heredoc (<<EOF … EOF) in the inline Dockerfile should be parsed and passed correctly into the build process, resulting in a valid /entrypoint.sh.