Don't fail /buildLayout if SupportFilesDirBase doesn't exist. (#2103)

This can occur on machines that haven't ever run PerfView before.

src/PerfView/Utilities/SupportFiles.cs

@@ -120,7 +120,11 @@ public static bool UnpackResourcesIfNeeded(bool force = false)
             // may not be in the EXE itself.  
             if (unpacked || File.Exists(Path.Combine(SupportFileDirBase, "CleanupNeeded")))
             {
-                Cleanup();
+                try
+                {
+                    Cleanup();
+                }
+                catch { } // Clean-up may fail if SupportFilesBaseDir doesn't exist.  This is especially true if we're running in a custom location or running /buildLayout.
             }
 
             return unpacked;