Windows: Fix docker device tool

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

contrib/docker-device-tool/device_tool.go

@@ -1,3 +1,5 @@
+// +build !windows
+
 package main
 
 import (

contrib/docker-device-tool/device_tool_windows.go

@@ -0,0 +1,4 @@
+package main
+
+func main() {
+}