Introduce containerd-shim-runhcs-v1 on Windows

Implements the containerd-shim-runhcs-v1 shim on Windows for the runtime
v2 shim API.

Signed-off-by: Justin Terry (VM) <juterry@microsoft.com>

vendor/github.com/Microsoft/hcsshim/internal/wclayer/createscratchlayer.go

@@ -0,0 +1,31 @@
+package wclayer
+
+import (
+	"github.com/Microsoft/hcsshim/internal/hcserror"
+	"github.com/sirupsen/logrus"
+)
+
+// CreateScratchLayer creates and populates new read-write layer for use by a container.
+// This requires both the id of the direct parent layer, as well as the full list
+// of paths to all parent layers up to the base (and including the direct parent
+// whose id was provided).
+func CreateScratchLayer(path string, parentLayerPaths []string) error {
+	title := "hcsshim::CreateScratchLayer "
+	logrus.Debugf(title+"path %s", path)
+
+	// Generate layer descriptors
+	layers, err := layerPathsToDescriptors(parentLayerPaths)
+	if err != nil {
+		return err
+	}
+
+	err = createSandboxLayer(&stdDriverInfo, path, 0, layers)
+	if err != nil {
+		err = hcserror.Errorf(err, title, "path=%s", path)
+		logrus.Error(err)
+		return err
+	}
+
+	logrus.Debugf(title+"- succeeded path=%s", path)
+	return nil
+}