Rebuild w/o IPv6

Is there an easy way to rebuild everything (kernel, base system and installed ports) w/o IPv6 support?

"NO_IPv6" hook in make.conf or something similar?
Create / update your /etc/src.conf file with the following:
Once done; do make buildworld
 make buildworld && make buildkernel && make installkernel
See handbook build world chapter and
Yes, do check out the proper way of building kernel and world, because the suggested order is incomplete. See /usr/src/Makefile for the 11-point list you should use.
Yes, thank you for pointing this out. I saw "make delete-old-libs" last night. My first rebuild was up to point #10 as it's shown /usr/src/UPDATING.
...Addition: Something is not clear. "delete-old" includes "delete-old-[files,dirs,libs]". Is point #11 redundant?
delete-old does *not* remove library files. delete-old-libs has to be run separately in order to delete library files.
I've just finished rebuilding world without IPv6 and saw that. Even though /usr/src/Makefile states:
"delete-old: deletes obsolete Directories/Files/Libraries"
issuing "make delete-old-libs" after "make delete-old" cleared some additional files.