driver/Darwin: Default to AAPCS for M-class CPUs.

 - This is an assumption that is currently hardwired into the backend, we need
   to do this in order for the frontend and backend to agree.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@166428 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed