nokogiri を bundle install する on Mavericks

# `nokogiri` を `bundle install` できるようにしたよ

## 概要

`nokogiri` が含まれている `Gemfile` で `bundle install` したら失敗した。

[Mac OS X Mavericksで”gem i nokogiri”失敗の解決方法 ](http://qiita.com/t_732_twit/items/a7956a170b1694f7ffc2) を参考に最低限の解決手順をメモしておく。

## 環境

* ruby 2.1.3
 * rbenv / ruby-build
* MacOS X 10.9.5
* Homebrew

## やったこと

* Homebrewのリポジトリ追加

```
% brew tap homebrew/dupes
```

* `libiconv` をインストール

```
% brew install libiconv
```

* `libxml2` をインストール

```
% brew install libxml2
% brew link --force libxml2
```

* `bundler` のビルドオプションを指定

```
% bundle config build.nokogiri --use-system-libraries
```


## エラーログ

* `libiconv` インストール前

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

    /Users/hiromu_shioya/.rbenv/versions/2.1.3/bin/ruby extconf.rb 
Building nokogiri using packaged libraries.
-----
libiconv is missing.  please visit http://nokogiri.org/tutorials/installing_nokogiri.html for help with installing dependencies.
-----
*** 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/hiromu_shioya/.rbenv/versions/2.1.3/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

extconf failed, exit code 1

Gem files will remain installed in /Users/hiromu_shioya/src/github.com/fastladder/fastladder/vendor/bundle/ruby/2.1.0/gems/nokogiri-1.6.3.1 for inspection.
Results logged to /Users/hiromu_shioya/src/github.com/fastladder/fastladder/vendor/bundle/ruby/2.1.0/extensions/x86_64-darwin-13/2.1.0-static/nokogiri-1.6.3.1/gem_make.out
An error occurred while installing nokogiri (1.6.3.1), and Bundler cannot continue.
Make sure that `gem install nokogiri -v '1.6.3.1'` succeeds before bundling.
```

* `libxml2` インストール前

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

    /Users/hiromu_shioya/.rbenv/versions/2.1.3/bin/ruby extconf.rb --use-system-libraries
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/hiromu_shioya/.rbenv/versions/2.1.3/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 /Users/hiromu_shioya/src/github.com/fastladder/fastladder/vendor/bundle/ruby/2.1.0/gems/nokogiri-1.6.3.1 for inspection.
Results logged to /Users/hiromu_shioya/src/github.com/fastladder/fastladder/vendor/bundle/ruby/2.1.0/extensions/x86_64-darwin-13/2.1.0-static/nokogiri-1.6.3.1/gem_make.out
An error occurred while installing nokogiri (1.6.3.1), and Bundler cannot continue.
Make sure that `gem install nokogiri -v '1.6.3.1'` succeeds before bundling.
```

## インストールできた！

`fastladder` が手元で動いたよやったー。