As a CNB user on Knative, I can use a PVC to cache builds

[ameyer-pivotal]

Acceptance Criteria
Case 1
When I configure a CNB build template for knative that uses a persistent volume claim as an interbuild cache
And The build complete successfully
Then The cache from that build is available to the next build that uses the same PVC

Case 2
When I configure a CNB build template for knative that uses a persistent volume claim as an interbuild cache
And The build fails or is otherwise interrupted at any point
Then The cache from that build is not available to the next build that uses the same PVC.

NOTES

• Update this repo with template and example for now. Make a note to create a PR to https://github.com/knative/build-templates after the next Lifecycle release

[ameyer-pivotal]

Knative template merged: knative/build-templates#119