如何访问Dockerfile中的共享卷？

Question

我正在从Cloud Build构建一个Docker映像，并尝试访问Dockerfile中的共享卷，但是找不到该卷。

运行pip安装root / build_cache / package_folder

- name: gcr.io/cloud-builders/gcloud
  id: clone_repo
  args: ['source', 'repos', 'clone', 'github_repository_name', '/build_cache']
  volumes:
  - name: 'build_cache'
    path: '/root/build_cache'
- name: 'gcr.io/cloud-builders/docker'
  args: ['build', '--network=cloudbuild', '-t', 'gcr.io/project/cloud_run-pubsub_example', './cloud-run/file_upserter/']
  waitFor: ['clone_repo']
  volumes:
  - name: 'build_cache'
    path: '/root/build_cache'


Error message:

Step #1: Step 3/7 : RUN pip install build_cache/package_folder
Step #1: ---> Running in fe3e0ee08746
Step #1: ERROR: Invalid requirement: 'build_cache/package_folder'
Step #1: Hint: It looks like a path. File 'build_cache/package_folder' does not exist.