Installing unpacked ruby gem

I am trying to install the cairo ruby gem on OSX 10.6. There seems to be a bug in the extconf.rb, which I've patched, but now I don't know how to create a gem, so I can install it... gem build folder won't work because there is no gemspec file or whatever (I've got absolutely no experience with gems^^), and gem install wants a .gem file...

These are the contents of my unpacked gem:

AUTHORS       ChangeLog     NEWS          Rakefile      e开发者_开发知识库xtconf.rb    pkg-config.rb src           test-unit
COPYING       GPL           README        doc           misc          samples       test

Thanks in advance for your help :)

Have you tried installing it as a plugin? Most gems have a git URI's you can use and do something like:

./script/plugin install abc