Fixes Missing SDKROOT for iOS+OFLib

When compiling the ```iOS+OFLib``` the ```SDKROOT``` was not being defined so it was having all sorts of trouble with the core framework locations (which require this variable).

![screen shot 2014-11-08 at 1 05 26 am](https://cloud.githubusercontent.com/assets/830748/4954072/8f075288-6688-11e4-824d-dfe97b2b1f76.png)
![screen shot 2014-11-08 at 1 05 38 am](https://cloud.githubusercontent.com/assets/830748/4954073/907f845a-6688-11e4-803e-5867f5a8de78.png)

It was falling into the ```/System/Frameworks``` which is incorrect, although it had some for OS X with the same name, always failed on iOS specific frameworks.