After upgrading to Rails 2.0.2 when trying to install the sqlite3-ruby gem got the following error:
ERROR: Error installing sqlite3-ruby: ERROR: Failed to build gem native extension. /usr/bin/ruby extconf.rb install sqlite3-ruby checking for sqlite3.h... no make make: *** No rule to make target `ruby.h', needed by `sqlite3_api_wrap.o'. Stop. Gem files will remain installed in /usr/lib/ruby/gems/1.8/gems/sqlite3-ruby-1.2.1 for inspection. Results logged to /usr/lib/ruby/gems/1.8/gems/sqlite3-ruby-1.2.1/ext/sqlite3_api/gem_make.out
In Mandriva you need to install the ruby-sqlite3 and the development libraries first, like:
sudo urpmi ruby-sqlite3 sudo urpmi libsqlite3-devel
After that you should be able to install the gem as normal.