OSX yosemite(10.10)でnokogiriのインストールに失敗

またしてもnokogiriのインストールに失敗しました。おのれnokogiri。

Gem::Ext::BuildError: ERROR: Failed to build gem native extension.

    /Users/hoge/.rbenv/versions/2.1.5/bin/ruby extconf.rb --use-system-libraries=true
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=/Users/val00300/.rbenv/versions/2.1.5/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=${xml2-dir}/include
    --with-xml2-lib
    --without-xml2-lib=${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-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
    --with-pkg-config
    --without-pkg-config

extconf failed, exit code 1

Gem files will remain installed in 
/workspace/.bundle/gems/ruby/2.1.0/gems/nokogiri-1.6.2.1 for inspection.
Results logged to 
/workspace/.bundle/gems/ruby/2.1.0/extensions/x86_64-darwin-14/2.1.0-static/nokogiri-1.6.2.1/gem_make.out
An error occurred while installing nokogiri (1.6.2.1), and Bundler cannot continue.
Make sure that `gem install nokogiri -v '1.6.2.1'` succeeds before bundling.

以下のコマンドを試したのですがうまくいきませんでした。
bundle configのオプションもいろいろ組み替えてうまくいかず...。

brew install libxml2 libxslt libiconv
brew link --force libxml2 libxslt libiconv
bundle config build.nokogiri --with-xml2-config=/usr/local/opt/libxml2/bin/xml2-config --with-xslt-config=/usr/local/opt/libxslt/bin/xslt-config --with-iconv-lib=/usr/local/opt/libiconv/lib --with-iconv-include=/usr/local/opt/libiconv/include --with-xml2-include=/usr/local/opt/libxml2/include --use-system-libraries=true

最終的に ここ にたどり着き、

bundle config build.nokogiri --with-xml2-include=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.10.sdk/usr/include/libxml2 --use-system-libraries

で解決。
理由はよくわかりませんが、HomeBrewで入れたlibxmll2ではなく、Xcodeの方のlibxml2を使わないとだめってことですね。

参考URL