@ScottE @mherrb You should have a look at what `--enable-ipv6` actually controls in packages. It's almost always just selecting between code-that-supports-ipv4-and-ipv6 and code-that-supports-ipv4 only.
There's really not an advantage to disabling IPv6 in most packages. If you want to disable IPv6, just turn it off in the kernel. That's the only thing you can reasonably do since many packages unconditionally support IPv6 anyway.