ProductUpgrader: use OrdinalIgnoreCase in exluded HashSet

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>

GVFS/GVFS.Common/ProductUpgrader.cs

@@ -183,7 +183,7 @@ namespace GVFS.Common
                 // directory causes a cycle(at some point we start copying C:\Program Files\GVFS\ProgramData\GVFS.Upgrade
                 // and its contents into C:\Program Files\GVFS\ProgramData\GVFS.Upgrade\Tools). The exclusion below is
                 // added to avoid this loop.
-               HashSet<string> directoriesToExclude = new HashSet<string>();
+               HashSet<string> directoriesToExclude = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
 
                 string secureDataRoot = GVFSPlatform.Instance.GetSecureDataRootForGVFS();
                 directoriesToExclude.Add(secureDataRoot);