hpricot 0.6 installation problem

[ksaito11]

$ sudo gem install hatenaapigraph
Bulk updating Gem source index for: http://gems.rubyforge.org
Successfully installed hatenaapigraph-0.2.2
Installing ri documentation for hatenaapigraph-0.2.2...
Installing RDoc documentation for hatenaapigraph-0.2.2...
$ sudo gem install hpricot
Select which gem to install for your platform (arm-linux)
 1. hpricot 0.6 (mswin32)
 2. hpricot 0.6 (jruby)
 3. hpricot 0.6 (ruby)
 4. hpricot 0.5 (ruby)
 5. hpricot 0.5 (mswin32)
 6. Skip this gem
 7. Cancel installation
> 3
Building native extensions.  This could take a while...
ERROR:  While executing gem ... (Gem::Installer::ExtensionBuildError)
    ERROR: Failed to build gem native extension.

ruby extconf.rb install hpricot
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/hpricot-0.6 for inspection.
Results logged to /var/lib/gems/1.8/gems/hpricot-0.6/ext/hpricot_scan/gem_make.out
$

$ uname -a
Linux debian10 2.6.12.6-arm1 #2 Thu Feb 8 15:00:20 JST 2007 armv5tejl GNU/Linux
$ ruby -v
ruby 1.8.5 (2006-08-25) [arm-linux]
$ gem -v
0.9.4
$

[ksaito11]

$ auto-apt search mkmf.rb
usr/lib/ruby/1.9/mkmf.rb        devel/ruby1.9-dev
usr/lib/ruby/1.8/mkmf.rb        devel/ruby1.8-dev
$ sudo aptitude install ruby1.8-dev

$ sudo gem install mechanize
Install required dependency hpricot? [Yn]
Select which gem to install for your platform (arm-linux)
 1. hpricot 0.6 (mswin32)
 2. hpricot 0.6 (jruby)
 3. hpricot 0.6 (ruby)
 4. hpricot 0.6 (jruby)
 5. hpricot 0.6 (ruby)
 6. hpricot 0.6 (mswin32)
 7. Skip this gem
 8. Cancel installation
> 3
Building native extensions.  This could take a while...
Successfully installed mechanize-0.6.9
Successfully installed hpricot-0.6
Installing ri documentation for mechanize-0.6.9...
Installing ri documentation for hpricot-0.6...
Installing RDoc documentation for mechanize-0.6.9...
Installing RDoc documentation for hpricot-0.6...
$