Reacting to CoreCLR package changes

test/dotnet-watch.FunctionalTests/project.json

@@ -13,6 +13,7 @@
     "Microsoft.DotNet.Watcher.Core": "1.0.0-*",
     "Microsoft.NETCore.Platforms": "1.0.1-*",
     "Newtonsoft.Json": "8.0.2",
+    "System.Threading": "4.0.11-*",
     "xunit": "2.1.0"
   },
   "frameworks": {