...
checking for nroff... /usr/bin/nroff
creating config.h
configure: creating ./config.status
config.status: creating Makefile
===>  Building for ruby-1.8.6,1
cd . && autoconf
autoconf: not found
*** Error code 127

Stop in /usr/ports/lang/ruby18/work/ruby-1.8.6.
*** Error code 1

Stop in /usr/ports/lang/ruby18.
*** Error code 1

Stop in /usr/ports/lang/ruby18.