Nokogiri gem on FreeBSD, libiconv missing error

If you try to install the nokogiri gem on freebsd you may get the following error message:

libiconv is missing.  please visit http://nokogiri.org/tutorials/installing_nokogiri.html for help with installing dependencies.

In that case it should suffice to use the following command to install the gem:

% gem install nokogiri -v 'DESIRED_VERSION' -- -with-iconv-lib=/usr/local/lib --with-iconv-include=/usr/local/include