Use multi-stage build for pytorch operator Dockerfile

[hmtai]

Now when user build pytorch operator image,he need build the pytorch operator binary first then use the Dockerfile to build the image.

Actually this can be built with docker multi-stage build to build the image only in one docker file.

[gaocegege]

Yeah, I think so.

/cc @johnugeorge

BTW, we should do it for tf-operator, too.

@hmtai Are you interested in the issue? I'd appreciate if you could help us.

[gaocegege]

/kind feature

[johnugeorge]

Closing the issue as PR is merge
/close

[k8s-ci-robot]

@johnugeorge: Closing this issue.

In response to this:

Closing the issue as PR is merge
/close

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