o Run make readmes (ports) from within CHROOTDIR to avoid pollution
and/or breakages due to /etc/make.conf on the host. Move it after make world and put it in an if-block so that we can include the commands in the script even if we're not going to make the readmes.
o When building docproj, make sure we propagate the setting of the
FTP_PASSIVE_MODE environment variable. Not propagating the envvar may cause fetch failures. This increases the number of cases for which one does not have to prefetch the packages.