how to resolve nokogiri 1.6.5 compile error

Building native extensions with: '--use-system-libraries'
This could take a while...
ERROR:  Error installing nokogiri:
    ERROR: Failed to build gem native extension.

    /usr/local/rvm/rubies/ruby-2.1.2/bin/ruby extconf.rb --use-system-libraries
checking if the C compiler accepts ... yes
checking if the C compiler accepts -Wno-error=unused-command-line-argument-hard-error-in-future... yes
Building nokogiri using system libraries.
libxml2 version 2.6.21 or later is required!
*** 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
    --without-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=/usr/local/rvm/rubies/ruby-2.1.2/bin/ruby
    --help
    --clean
    --use-system-libraries
    --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-xml2-dir
    --without-xml2-dir
    --with-xml2-include
    --without-xml2-include=${xml2-dir}/include
    --with-xml2-lib
    --without-xml2-lib=${xml2-dir}/lib
    --with-libxml-2.0-config
    --without-libxml-2.0-config
    --with-pkg-config
    --without-pkg-config
    --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-exslt-dir
    --without-exslt-dir
    --with-exslt-include
    --without-exslt-include=${exslt-dir}/include
    --with-exslt-lib
    --without-exslt-lib=${exslt-dir}/lib
    --with-libexslt-config
    --without-libexslt-config

extconf failed, exit code 1

Gem files will remain installed in /usr/local/rvm/gems/ruby-2.1.2/gems/nokogiri-1.6.5 for inspection.
Results logged to /usr/local/rvm/gems/ruby-2.1.2/extensions/x86_64-darwin-13/2.1.0-static/nokogiri-1.6.5/gem_make.out

OS X에서 metasploit을 사용하려는데 bundle install을 해주라길래 해줬는데 자꾸 에러를 내뱉어서 찾아본 방법이다.

결과는 xcode를 전에 지웠었는데.. 다시 설치해주고 xcode에 저장된 library(libxml2)를 사용하면 되는 것이었다..

gem install nokogiri -v '1.6.5' -- --use-system-libraries=true --with-xml2-include=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/include/libxml2

그러므로 이렇게 해주면 정상적으로 설치 완료.. 고생이 많았다..ㅠ