Gems dependencies

slave:~# gem install god
Bulk updating Gem source index for: http://gems.rubyforge.org/
Building native extensions. This could take a while…
ERROR: Error installing god:
ERROR: Failed to build gem native extension./usr/bin/ruby1.8 extconf.rb install god
extconf.rb:1:in `require’: no such file to load — mkmf (LoadError)
from extconf.rb:1

Gem files will remain installed in /var/lib/gems/1.8/gems/god-0.7.8 for inspection.
Results logged to /var/lib/gems/1.8/gems/god-0.7.8/ext/god/gem_make.out

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Solution: Install dev libraries.

slave:~# sudo apt-get install ruby1.8-dev linux-libc-dev libc6-dev