This is done so that the following compiles with no warnings:
int fn(type_10_12) __attribute__((availability(macos, introduced=10.12)));

Differential revision: https://reviews.llvm.org/D25284

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@285457 91177308-0d34-0410-b5e6-96231b3b80d8