You can still have two builds if you want, one with IPv6 enabled and one without it. Most likely unnecessary, but someone who used IPv4-only build so far, might be a little surprised, when it suddenly starts listening on IPv6 too. Not that it could hurt by itself.
Just don't try to enable mapped adddresses, there is still one (different) bug there. Or at least it was about three months ago, when I last checked. And since it's the same one I already encountered back in 2008, I guess it's still there now.
When Apache is configured to listen on any address, it makes it into 0.0.0.0 and ::. With mapped addresses it drops 0.0.0.0, because IPv4 is handled by IPv6 socket. But there's some problem when list of sockets it passed to child process. I don't remember exactly, but it's either that child incorrectly expects one more address (including the dropped 0.0.0.0) or parent passes it when child does not expect it.
I never had enough time to fix it or at least properly understand it, because it's not just simple dealing with network stuff, it requires deeper knowledge about insides of httpd.