gem install ruby_kml - failed to build native extension -- Mac with OSX 10.9.4, ruby 1.9.3

[larrytalley]

Trying to install on my Mac with OSX 10.9.4, Ruby 1.9.3p448:

gem install ruby_kml
Building native extensions. This could take a while...
Building nokogiri using packaged libraries.
ERROR: Error installing ruby_kml:
ERROR: Failed to build gem native extension.

/Users/ltalley/.rvm/rubies/ruby-1.9.3-p448/bin/ruby extconf.rb

Building nokogiri using packaged libraries.
checking for iconv.h... *** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers. Check the mkmf.log file for more
details. You may need configuration options.

Provided configuration options:
--with-opt-dir
--with-opt-include
--without-opt-include=${opt-dir}/include
--with-opt-lib
--without-opt-lib=${opt-dir}/lib
--with-make-prog
--without-make-prog
--srcdir=.
--curdir
--ruby=/Users/ltalley/.rvm/rubies/ruby-1.9.3-p448/bin/ruby
--help
--clean
--use-system-libraries
--enable-static
--disable-static
--with-zlib-dir
--without-zlib-dir
--with-zlib-include
--without-zlib-include=${zlib-dir}/include
--with-zlib-lib
--without-zlib-lib=${zlib-dir}/lib
--enable-cross-build
--disable-cross-build
/Users/ltalley/.rvm/rubies/ruby-1.9.3-p448/lib/ruby/1.9.1/mkmf.rb:381:in try_do': The compiler failed to generate an executable file. (RuntimeError) You have to install development tools first. from /Users/ltalley/.rvm/rubies/ruby-1.9.3-p448/lib/ruby/1.9.1/mkmf.rb:506:intry_cpp'
from /Users/ltalley/.rvm/rubies/ruby-1.9.3-p448/lib/ruby/1.9.1/mkmf.rb:931:in block in have_header' from /Users/ltalley/.rvm/rubies/ruby-1.9.3-p448/lib/ruby/1.9.1/mkmf.rb:790:inblock in checking_for'
from /Users/ltalley/.rvm/rubies/ruby-1.9.3-p448/lib/ruby/1.9.1/mkmf.rb:284:in block (2 levels) in postpone' from /Users/ltalley/.rvm/rubies/ruby-1.9.3-p448/lib/ruby/1.9.1/mkmf.rb:254:inopen'
from /Users/ltalley/.rvm/rubies/ruby-1.9.3-p448/lib/ruby/1.9.1/mkmf.rb:284:in block in postpone' from /Users/ltalley/.rvm/rubies/ruby-1.9.3-p448/lib/ruby/1.9.1/mkmf.rb:254:inopen'
from /Users/ltalley/.rvm/rubies/ruby-1.9.3-p448/lib/ruby/1.9.1/mkmf.rb:280:in postpone' from /Users/ltalley/.rvm/rubies/ruby-1.9.3-p448/lib/ruby/1.9.1/mkmf.rb:789:inchecking_for'
from /Users/ltalley/.rvm/rubies/ruby-1.9.3-p448/lib/ruby/1.9.1/mkmf.rb:930:in have_header' from extconf.rb:103:inhave_iconv?'