Walk the decls looking for the last one that has an attribute. We do have to walk

them, otherwise we cannot produce an error for both

struct HIDDEN test4; // canonical
struct test4;
struct DEFAULT test4;

and

struct test5; // canonical
struct HIDDEN test5;
struct DEFAULT test5;

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@156016 91177308-0d34-0410-b5e6-96231b3b80d8