I found this:
Changing Compiler to llvm-clang on existing iPhone Project
But that does not help.
I am still getting the error. Setting the BaseSDK to the iPhoneSimulator 3.1 seems to work. But I don't think this is the right thing to do...
If you read the answer and comments on that question, you'll see that there is not yet a version of LLVM that will target the iPhone device. You can target the iPhone Simulator using LLVM GCC, with some fiddling, because that is running on a Mac. Even though LLVM can target the ARM platform, Apple has indicated that it's not yet ready for use in deploying to the iPhone.
来源:https://stackoverflow.com/questions/1525510/changing-to-llvm-compiler-when-deploying-iphone-app