nanoFramework: Fix getting latest preview of mscorlib nuget

-preview.4 was ordrered before -preview.11.

Author: angularsen

CodeGen/Generators/NanoFrameworkGenerator.cs

@@ -67,7 +67,7 @@ public static void Generate(string rootDir, Quantity[] quantities)
 
             // NuGet package Version
             // including preview
-            var mscorlibPackage = packageVersions.Where(v => v.IsPrerelease).OrderByDescending(v => v.Version).First();
+            var mscorlibPackage = packageVersions.Where(v => v.IsPrerelease).OrderByDescending(v => v).First();
             // stable only
             //var mscorlibPackage = packageVersions.OrderByDescending(v => v.Version).First();