Update link for local container builder

CONTRIBUTING.md

@@ -17,7 +17,7 @@ Please see https://git.k8s.io/community/CLA.md for more info
 
 Setup:
 
-- Download [google container builder]
+- Download [google container builder](https://cloud.google.com/container-builder/docs/build-debug-locally)
 - Export `GOOS` (darwin/linux) and `GOARCH` (amd64) vars to match the system to build
 - Export `OUTPUT` to a location to write the directory containing the final build artifacts
 
@@ -55,4 +55,4 @@ You can reach the maintainers of this project at:
 
 Participation in the Kubernetes community is governed by the [Kubernetes Code of Conduct](code-of-conduct.md).
 
-[google container builder]: https://github.com/kubernetes-sigs/container-builder-local
+[google container builder]: https://github.com/kubernetes-sigs/container-builder-local