/usr/lib/ruby/vendor_ruby/ is in ruby-cairo 1.10.0-3.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/1.8/
/usr/lib/ruby/vendor_ruby/1.8/x86_64-linux/
/usr/lib/ruby/vendor_ruby/1.8/x86_64-linux/cairo.so
/usr/lib/ruby/vendor_ruby/1.8/x86_64-linux/rb_cairo.h
/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/cairo.so
/usr/lib/ruby/vendor_ruby/1.9.1/x86_64-linux/rb_cairo.h
/usr/lib/ruby/vendor_ruby/cairo.rb
/usr/lib/ruby/vendor_ruby/cairo/
/usr/lib/ruby/vendor_ruby/cairo/paper.rb
/usr/lib/ruby/vendor_ruby/cairo/point.rb
/usr/lib/ruby/vendor_ruby/cairo/color.rb
/usr/lib/ruby/vendor_ruby/cairo/constants.rb
/usr/lib/ruby/vendor_ruby/cairo/context.rb
/usr/lib/ruby/vendor_ruby/cairo/papers.rb
/usr/lib/ruby/vendor_ruby/cairo/colors.rb
/usr/lib/ruby/vendor_ruby/cairo/path.rb
/usr/lib/ruby/vendor_ruby/cairo/context/
/usr/lib/ruby/vendor_ruby/cairo/context/color.rb
/usr/lib/ruby/vendor_ruby/cairo/context/triangle.rb
/usr/lib/ruby/vendor_ruby/cairo/context/blur.rb
/usr/lib/ruby/vendor_ruby/cairo/context/rectangle.rb
/usr/lib/ruby/vendor_ruby/cairo/context/path.rb
/usr/lib/ruby/vendor_ruby/cairo/context/circle.rb
/usr/lib/ruby/vendor_ruby/1.8/cairo.rb