在这里详述 ruby/custom_require.rb:36:in `require': cannot load such file -- mkmf (LoadError)。

{{{ root@x201i:/home/l# gem install classifier Building native extensions. This could take a while... ERROR: Error installing classifier: ERROR: Failed to build gem native extension.

    /usr/bin/ruby1.9.1 extconf.rb

/usr/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in require': cannot load such file -- mkmf ...