code: def _write_buildproc_yaml(build_data, env, user, cmd, volumes, app_folder):
      
  
      buildproc = ProcData({
          'app_folder': str(app_folder),
          'app_name': build_data.app_name,
          'app_repo_url': '',
          'app_repo_type': '',
          'buildpack_url': '',
          'buildpack_version': '',
          'config_name': 'build',
          'env': env,
          'host': '',
          'port': 0,
          'version': build_data.version,
          'release_hash': '',
          'settings': {},
          'user': user,
          'cmd': cmd,
          'volumes': volumes,
          'proc_name': 'build',
          'image_name': build_data.image_name,
          'image_url': build_data.image_url,
          'image_md5': build_data.image_md5,
      })
  
      # write a proc.yaml for the container.
      with open('buildproc.yaml', 'w') as f:
          f.write(buildproc.as_yaml())
      return get_container_path(buildproc)
docs: Write a proc.yaml for the container and return the container path