sqlite3-rubyのインストール

以下のようなエラーが出た場合は

example% sudo gem install sqlite3-ruby
Building native extensions. This could take a while...
ERROR: Error installing sqlite3-ruby:
ERROR: Failed to build gem native extension.

/usr/local/bin/ruby extconf.rb
checking for fdatasync() in -lrt... yes
checking for sqlite3.h... no

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/bin/ruby
--with-sqlite3-dir
--without-sqlite3-dir
--with-sqlite3-include
--without-sqlite3-include=${sqlite3-dir}/include
--with-sqlite3-lib
--without-sqlite3-lib=${sqlite3-dir}/lib
--with-rtlib
--without-rtlib

Gem files will remain installed in /usr/local/lib/ruby/gems/1.9.1/gems/sqlite3-ruby-1.2.5 for inspection.
Results logged to /usr/local/lib/ruby/gems/1.9.1/gems/sqlite3-ruby-1.2.5/ext/sqlite3_api/gem_make.out

SQLite 3 開発用ファイルをインストールしてからインストールする

sudo apt-get install libsqlite3-dev