/usr/lib/ruby/ is in ruby-gnome2-dev 2.1.0-1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/
/usr/lib/ruby/vendor_ruby/1.9.1/
/usr/lib/ruby/vendor_ruby/1.9.1/x86_64-linux/
/usr/lib/ruby/vendor_ruby/1.9.1/x86_64-linux/glib-enum-types.h
/usr/lib/ruby/vendor_ruby/1.9.1/x86_64-linux/rb-gobject-introspection.h
/usr/lib/ruby/vendor_ruby/1.9.1/x86_64-linux/rbatk.h
/usr/lib/ruby/vendor_ruby/1.9.1/x86_64-linux/rbatkversion.h
/usr/lib/ruby/vendor_ruby/1.9.1/x86_64-linux/rbgcompat.h
/usr/lib/ruby/vendor_ruby/1.9.1/x86_64-linux/rbgdk-pixbuf.h
/usr/lib/ruby/vendor_ruby/1.9.1/x86_64-linux/rbgdk-pixbuf2conversions.h
/usr/lib/ruby/vendor_ruby/1.9.1/x86_64-linux/rbgdk.h
/usr/lib/ruby/vendor_ruby/1.9.1/x86_64-linux/rbgdk3.h
/usr/lib/ruby/vendor_ruby/1.9.1/x86_64-linux/rbgdk3conversions.h
/usr/lib/ruby/vendor_ruby/1.9.1/x86_64-linux/rbgdkconversions.h
/usr/lib/ruby/vendor_ruby/1.9.1/x86_64-linux/rbgio2.h
/usr/lib/ruby/vendor_ruby/1.9.1/x86_64-linux/rbgio2conversions.h
/usr/lib/ruby/vendor_ruby/1.9.1/x86_64-linux/rbglib.h
/usr/lib/ruby/vendor_ruby/1.9.1/x86_64-linux/rbglib2conversions.h
/usr/lib/ruby/vendor_ruby/1.9.1/x86_64-linux/rbglibdeprecated.h
/usr/lib/ruby/vendor_ruby/1.9.1/x86_64-linux/rbgobject.h
/usr/lib/ruby/vendor_ruby/1.9.1/x86_64-linux/rbgtk.h
/usr/lib/ruby/vendor_ruby/1.9.1/x86_64-linux/rbgtk3.h
/usr/lib/ruby/vendor_ruby/1.9.1/x86_64-linux/rbgtk3conversions.h
/usr/lib/ruby/vendor_ruby/1.9.1/x86_64-linux/rbgtkconversions.h
/usr/lib/ruby/vendor_ruby/1.9.1/x86_64-linux/rbgtkmacros.h
/usr/lib/ruby/vendor_ruby/1.9.1/x86_64-linux/rbgutil.h
/usr/lib/ruby/vendor_ruby/1.9.1/x86_64-linux/rbgutil_list.h
/usr/lib/ruby/vendor_ruby/1.9.1/x86_64-linux/rbgutildeprecated.h
/usr/lib/ruby/vendor_ruby/1.9.1/x86_64-linux/rbpango.h
/usr/lib/ruby/vendor_ruby/1.9.1/x86_64-linux/rbpangoconversions.h
/usr/lib/ruby/vendor_ruby/1.9.1/x86_64-linux/rbpangoversion.h
/usr/lib/ruby/vendor_ruby/glib-mkenums.rb
/usr/lib/ruby/vendor_ruby/gnome2-raketask.rb
/usr/lib/ruby/vendor_ruby/mkmf-gnome2.rb