fluentdのpluginを入れる際の注意点

プラグインを入れる際下記のようなエラーになっていろいろ調べたけど最初わからなかった。
ruby/thread.hの行でエラーになってるっぽいのでちゃんとincludeされてないのかとか思ったけど実際は違って、
結局gccが足りなかったということだった。
別環境ではインストールできていたのでなぜなのか気づくのに時間かかった・・・。

Building native extensions.  This could take a while...
ERROR:  Error installing fluent-plugin-mysql_explain:
        ERROR: Failed to build gem native extension.

    /opt/td-agent/embedded/bin/ruby -r ./siteconf20160901-9025-102pzis.rb extconf.rb
checking for ruby/thread.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=/opt/td-agent/embedded/bin/ruby
/opt/td-agent/embedded/lib/ruby/2.1.0/mkmf.rb:467:in `try_do': The compiler failed to generate an executable file. (RuntimeError)
You have to install development tools first.
        from /opt/td-agent/embedded/lib/ruby/2.1.0/mkmf.rb:598:in `try_cpp'
        from /opt/td-agent/embedded/lib/ruby/2.1.0/mkmf.rb:1072:in `block in have_header'
        from /opt/td-agent/embedded/lib/ruby/2.1.0/mkmf.rb:923:in `block in checking_for'
        from /opt/td-agent/embedded/lib/ruby/2.1.0/mkmf.rb:351:in `block (2 levels) in postpone'
        from /opt/td-agent/embedded/lib/ruby/2.1.0/mkmf.rb:321:in `open'
        from /opt/td-agent/embedded/lib/ruby/2.1.0/mkmf.rb:351:in `block in postpone'
        from /opt/td-agent/embedded/lib/ruby/2.1.0/mkmf.rb:321:in `open'
        from /opt/td-agent/embedded/lib/ruby/2.1.0/mkmf.rb:347:in `postpone'
        from /opt/td-agent/embedded/lib/ruby/2.1.0/mkmf.rb:922:in `checking_for'
        from /opt/td-agent/embedded/lib/ruby/2.1.0/mkmf.rb:1071:in `have_header'
        from extconf.rb:16:in `<main>'

extconf failed, exit code 1

Gem files will remain installed in /opt/td-agent/embedded/lib/ruby/gems/2.1.0/gems/mysql2-0.4.4 for inspection.
Results logged to /opt/td-agent/embedded/lib/ruby/gems/2.1.0/extensions/x86_64-linux/2.1.0/mysql2-0.4.4/gem_make.out