Add BuildTemplate for makisu

[johscheuer]

This PR adds a simple BuildTemplate for makisu (https://github.com/uber/makisu). As soon as https://github.com/knative/build/pull/550 gets merged I would adjust the Secret Volume to be rendered by a Template Parameter rather than a hardcoded string.

Currently the makisu setup doesn't use a global build cache (mentioned here: https://github.com/uber/makisu#using-cache) if you want I can add an example for the global cache too.

Fixes: https://github.com/knative/build-templates/issues/77

[knative-prow-robot]

Hi @johscheuer. Thanks for your PR.

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[johscheuer]

ping @ImJasonH and @mattmoor

[imjasonh]

/lgtm /approve

[imjasonh]

/lgtm

[knative-prow-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ImJasonH, johscheuer

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