Windows: Docker build starting to work

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

chrootarchive/archive_windows.go

@@ -1,6 +1,21 @@
 package chrootarchive
 
+import (
+	"io"
+
+	"github.com/docker/docker/pkg/archive"
+)
+
 // chroot is not supported by Windows
 func chroot(path string) error {
 	return nil
 }
+
+func invokeUnpack(decompressedArchive io.ReadCloser,
+	dest string,
+	options *archive.TarOptions) error {
+	// Windows is different to Linux here because Windows does not support
+	// chroot. Hence there is no point sandboxing a chrooted process to
+	// do the unpack. We call inline instead within the daemon process.
+	return archive.Unpack(decompressedArchive, dest, options)
+}