Suggest to the user to define a cache volume for bazel

[bhack]

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URL(s) with the issue:

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Description of issue (what needs changing):

We the current info about Docker build from source we will lost the cache when we destroy the container

Clear description

The bazel cache will be stored in /root/.cache/bazel/ that it is ephemeral and so it will lost if the container it is removed. So you are going to lost hours of builds just if you will restart the image with a new container. You need to suggest to mount an host volume for the bazel cache.

For example, why should someone use this method? How is it useful?