On Darwin, the linker removes functions in CommentDumper.o (Comment::dump())

despite __attribute__(__used__).  As explained by Argyrios,
> .a archive files do some stripping of their own and they remove .o files that
> contain functions that are not referenced by any other .o file.

The fix is to use these functions from another .o file.

Thanks, Argyrios!

llvm-svn: 160437