Many headers in MacOSX10.13.sdk are empty links

[ddobrev]

IOReturn.h, IOKitKeys.h, IOHIDTypes.h, IOLLEvent.h, to name a few. Basically, almost all links. Might be related to #15.

[yinyinnie]

I meet this problem too When I builded AOSP on my Mac. At last, I used the MacOSX10.12.sdk to build AOSP, and It done.