Cannot install tiny_tds on os.x 10.9.4

问题

I'm trying to install tiny_tds on a mac running OS.X Mavericks but I receive the following error:

ERROR:  Error installing tiny_tds:
ERROR: Failed to build gem native extension.

/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby extconf.rb gem install tiny_tds -- --without-iconvlib --with-freetds-lib=/usr/local/Cellar/freetds/0.91/lib --with-freetds-include=/usr/local/Cellar/freetds/0.91/include
checking for iconv_open() in iconv.h... no
checking for iconv_open() in -lfalse... no
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libiconv is missing.
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*** extconf.rb failed ***

I'm using the following command to install tiny_tds:

sudo gem install tiny_tds -- --with-freetds-include=/usr/local/include --with-freetds-lib=/usr/local/lib --with-iconv-include=/usr/local/Cellar/libiconv/1.14/include --with-iconv-lib=/usr/local/Cellar/libiconv/1.14/lib

I have looked into iconv.h and there is no iconv_open() method.

By the way, I'm using ruby 2.0.0p451