Adding parameterization to go-runner Dockerfile

[jeremyrickard]

Signed-off-by: Jeremy Rickard jrickard@microsoft.com

What type of PR is this?

/kind feature

What this PR does / why we need it:

This PR updates the go-runner Dockerfile to support better overriding of the builder and base images used. BUILDER_IMAGE becomes an ARG and a new Makefile variable DISTROLESS_REGISRTRY is added to allow the DISTROLESS_IMAGE build arg to receive the registry/repo as well. This is defaulted to gcr.io/distroless to not impact the existing configurations. The DISTROLESS_IMAGE build arg is populated with a combination of the DISTROLESS_REGISTRY and DISTROLESS_IMAGE Makefile variables:

BUILD_ARGS = --build-arg=BUILDER_IMAGE=$(BUILDER_IMAGE) \
             --build-arg=DISTROLESS_IMAGE=$(DISTROLESS_REGISTRY)/$(DISTROLESS_IMAGE)

This allows you to completely override the build-arg but is backward compatible w/ the existing variants.yml and the cloudbuild.yaml

GO_VERSION and OS_CODENAME are no longer needed within the Dockerfile and are expressed entirely within the Makefile.

Which issue(s) this PR fixes:

Fixes #2702

Special notes for your reviewer:

Does this PR introduce a user-facing change?

 BUILDER_IMAGE can now be overridden when building the go-runner image. Additionally a new variable DISTROLESS_REGISTRY can be used to specify a different registry and repository, to more completely override the DISTROLESS_IMAGE build arg to support custom images. 

[cpanato]

/lgtm

thanks

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cpanato, jeremyrickard, saschagrunert

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• images/build/go-runner/OWNERS [cpanato,jeremyrickard,saschagrunert]

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