There were two problems with this testcase: we weren't copying the target
attribute from the second declaration to the global alias for the first
one (duplicate_decls hunk), and then we were treating the third one as
matching the earlier one even though both are versioned (decls_match hunk).
The latter change required a fix to find_last_decl (used for attribute
mismatch warnings) to give up if we see a versioned function, as in that
case we can't determine whether the decls match, because we are still in the
process of setting the attributes on the new decl.
PR c++/104669
gcc/cp/ChangeLog:
* decl.c (decls_match): Compare versions even if not recording.
(duplicate_decls): Propagate attributes to alias.
* decl2.c (find_last_decl): Give up if versioned.