MacOSをmavericksにアップグレードしたらnokogiriをインストールできなくなった。


必要なライブラリがないと怒られる

````bash:
Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.

    /Users/me/.rvm/rubies/ruby-1.9.3-p429/bin/ruby extconf.rb
Extracting libxml2-2.8.0.tar.gz into tmp/x86_64-apple-darwin13.0.0/ports/libxml2/2.8.0... OK
Running 'configure' for libxml2 2.8.0... OK
Running 'compile' for libxml2 2.8.0... OK
Running 'install' for libxml2 2.8.0... OK
Activating libxml2 2.8.0 (from /Users/me/.rvm/gems/ruby-1.9.3-p429@myapp/gems/nokogiri-1.6.0/ports/x86_64-apple-darwin13.0.0/libxml2/2.8.0)...
Extracting libxslt-1.1.26.tar.gz into tmp/x86_64-apple-darwin13.0.0/ports/libxslt/1.1.26... OK
Running 'configure' for libxslt 1.1.26... OK
Running 'compile' for libxslt 1.1.26... OK
Running 'install' for libxslt 1.1.26... OK
Activating libxslt 1.1.26 (from /Users/me/.rvm/gems/ruby-1.9.3-p429@myapp/gems/nokogiri-1.6.0/ports/x86_64-apple-darwin13.0.0/libxslt/1.1.26)...
checking for libxml/parser.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/me/.rvm/rubies/ruby-1.9.3-p429/bin/ruby
	--with-zlib-dir
	--without-zlib-dir
	--with-zlib-include
	--without-zlib-include=${zlib-dir}/include
	--with-zlib-lib
	--without-zlib-lib=${zlib-dir}/lib
	--with-iconv-dir
	--without-iconv-dir
	--with-iconv-include
	--without-iconv-include=${iconv-dir}/include
	--with-iconv-lib
	--without-iconv-lib=${iconv-dir}/lib
	--with-xml2-dir
	--without-xml2-dir
	--with-xml2-include
	--without-xml2-include=${xml2-dir}/include
	--with-xml2-lib
	--without-xml2-lib=${xml2-dir}/lib
	--with-xslt-dir
	--without-xslt-dir
	--with-xslt-include
	--without-xslt-include=${xslt-dir}/include
	--with-xslt-lib
	--without-xslt-lib=${xslt-dir}/lib
	--with-libxslt-config
	--without-libxslt-config
	--with-pkg-config
	--without-pkg-config
	--with-libxml-2.0-config
	--without-libxml-2.0-config
	--with-libiconv-config
	--without-libiconv-config
/Users/me/.rvm/rubies/ruby-1.9.3-p429/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/me/.rvm/rubies/ruby-1.9.3-p429/lib/ruby/1.9.1/mkmf.rb:506:in `try_cpp'
	from /Users/me/.rvm/rubies/ruby-1.9.3-p429/lib/ruby/1.9.1/mkmf.rb:970:in `block in find_header'
	from /Users/me/.rvm/rubies/ruby-1.9.3-p429/lib/ruby/1.9.1/mkmf.rb:790:in `block in checking_for'
	from /Users/me/.rvm/rubies/ruby-1.9.3-p429/lib/ruby/1.9.1/mkmf.rb:284:in `block (2 levels) in postpone'
	from /Users/me/.rvm/rubies/ruby-1.9.3-p429/lib/ruby/1.9.1/mkmf.rb:254:in `open'
	from /Users/me/.rvm/rubies/ruby-1.9.3-p429/lib/ruby/1.9.1/mkmf.rb:284:in `block in postpone'
	from /Users/me/.rvm/rubies/ruby-1.9.3-p429/lib/ruby/1.9.1/mkmf.rb:254:in `open'
	from /Users/me/.rvm/rubies/ruby-1.9.3-p429/lib/ruby/1.9.1/mkmf.rb:280:in `postpone'
	from /Users/me/.rvm/rubies/ruby-1.9.3-p429/lib/ruby/1.9.1/mkmf.rb:789:in `checking_for'
	from /Users/me/.rvm/rubies/ruby-1.9.3-p429/lib/ruby/1.9.1/mkmf.rb:969:in `find_header'
	from extconf.rb:166:in `<main>'


Gem files will remain installed in /Users/me/.rvm/gems/ruby-1.9.3-p429@myapp/gems/nokogiri-1.6.0 for inspection.
Results logged to /Users/me/.rvm/gems/ruby-1.9.3-p429@myapp/gems/nokogiri-1.6.0/ext/nokogiri/gem_make.out

An error occurred while installing nokogiri (1.6.0), and Bundler cannot continue.
Make sure that `gem install nokogiri -v '1.6.0'` succeeds before bundling.
````

homebrewをアップグレードして、brew doctorで言われた通りに対処する。

````bash:
brew upgrade
brew doctor
````

````bash:
bundle install
````