[osx-port] fix can't detect apple clang 4.2 vs. clang 3.2
[osx-port] fix can't detect apple clang 4.2 vs. clang 3.2

xzero/x0,christianparpart/x0,christianparpart/x0,xzero/x0,xzero/x0,xzero/x0,christianparpart/x0,xzero/x0,christianparpart/x0,xzero/x0,christianparpart/x0,christianparpart/x0,christianparpart/x0