Error while installing RubyGems

Error :

/usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `gem_original_require’: no such file to load — zlib (LoadError)

Fix :

Ruby-zlib should be built into Ruby 1.8
Build ruby-zlib manually.

wget http://www.blue.sky.or.jp/atelier/ruby/ruby-zlib-0.6.0.tar.gz
tar xvzf ruby-zlib-0.6.0.tar.gz
cd ruby-zlib-0.6.0
ruby extconf.rb
make
make install

Now, reinstall Ruby Gems from source.