Meson: Warn when IPv6 not enabled
With autotools we have lack of IPv6 support as a hard error, unless explicitly allowed, since freeciv-3.0. Thus it's a bit weird that meson build now silently disables IPv6. Make it at least warn in that case.
With autotools we have lack of IPv6 support as a hard error, unless explicitly allowed, since freeciv-3.0. Thus it's a bit weird that meson build now silently disables IPv6. Make it at least warn in that case.