Create physical SupportingFiles folder

Riot/SupportingFiles/empty.mm

@@ -0,0 +1,26 @@
+/*
+ Copyright 2015 OpenMarket Ltd
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+ */
+
+#import <Foundation/Foundation.h>
+
+/*
+ This file exists only to force Xcode to use the GNU c++ standard library (libstdc++).
+ Even if the project settings indicate they want to use libstdc++, if there is no .mm file, Xcode
+ continues to use its c++ lib. That prevents the app from linking if it includes some .hh files.
+
+ @see: http://stackoverflow.com/a/19250215/3936576
+
+ */