ruby.inc: DEPEND on libyaml-native

Without this dependency we will see warnings when ever we use the
ruby-native from the sysroot

  ...tmp/sysroots/x86_64-linux/usr/lib/ruby/yaml.rb:84:in `<top (required)>':
  It seems your ruby installation is missing psych (for YAML output).
  To eliminate this warning, please install libyaml and reinstall your ruby.

Signed-off-by: Mark Asselstine <mark.asselstine@windriver.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>