Solved How-to prevent builds with IP6

I do not need and don't want IP6 network configuration in my home network. So I have configured all interfaces as IP4 only - and that works very well for me.

My problem is, when I build ports, they often have something like -DHAVE_IP6 or or -DINET6 as parameters in the Makefiles ( on all levels of the port ). And so they try to build with IP6 in mind, which of course doesn't work all the time.

Is there any trick in /etc/make.conf or other places to tell centrally all builds, that IP6 is not available ?