Windows CI: Setup for testing against Windows

Signed-off-by: John Howard <jhoward@microsoft.com>

hack/make/.ensure-frozen-images-windows

@@ -0,0 +1,25 @@
+#!/bin/bash
+set -e
+
+# This scripts sets up the required images for Windows to Windows CI
+
+# Tag windowsservercore as latest
+set +e
+! BUILD=$(docker images | grep windowsservercore | grep -v latest | awk '{print $2}')
+if [ -z $BUILD ]; then
+	echo "ERROR: Could not find windowsservercore images"
+	exit 1
+fi
+
+! LATESTCOUNT=$(docker images | grep windowsservercore | grep -v $BUILD | wc -l)
+if [ $LATESTCOUNT -ne 1 ]; then
+	set -e
+	docker tag windowsservercore:$BUILD windowsservercore:latest
+	echo "INFO: Tagged windowsservercore:$BUILD with latest"
+fi
+
+# Busybox (requires windowsservercore)
+if [ -z "$(docker images | grep busybox)" ]; then
+	echo "INFO: Building busybox"
+	docker build -t busybox https://raw.githubusercontent.com/jhowardmsft/busybox/master/Dockerfile
+fi