It takes ~50 minutes to build kubernetes from source for Windows presubmits

[mauriciopoppe]

Example: https://prow.k8s.io/view/gs/kubernetes-ci-logs/pr-logs/pull/kubernetes-sigs_gcp-compute-persistent-disk-csi-driver/1951/pull-gcp-compute-persistent-disk-csi-driver-e2e-windows-2019/1894527667919654912

The integration script is called with

+ /home/prow/go/src/sigs.k8s.io/gcp-compute-persistent-disk-csi-driver/bin/k8s-integration-test ... --kube-version=master ...

Which together with the flag flag.Bool("do-k8s-build", true, "building the driver from source. If false, will fetch precompiled artifacts")

Forces to build k8s from scratch

gcp-compute-persistent-disk-csi-driver/test/k8s-integration/main.go

Lines 330 to 335 in 39a5910

	if *doK8sBuild {
	klog.Info("Building Kubernetes source")
	if err := buildKubernetes(testParams.k8sSourceDir, "quick-release"); err != nil {
	return fmt.Errorf("failed to build Kubernetes: %v", err.Error())
	}
	} else {

Which takes ~50 minutes:

I0225 23:48:36.829509   17242 main.go:331] Building Kubernetes source
...
I0226 00:35:01.275869   17242 utils.go:15] Starting E2E Cluster on GCE

Do we need to build k/k from source or just take the latest CI builds? I think we should take the k/k CI builds, I forgot the reason we build from source.