/usr/lib/x86_64-linux-gnu/ruby/ is in ruby-gnome2-dev 2.1.0-1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.0.0/
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.0.0/glib-enum-types.h
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.0.0/rb-gobject-introspection.h
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.0.0/rbatk.h
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.0.0/rbatkversion.h
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.0.0/rbgcompat.h
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.0.0/rbgdk-pixbuf.h
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.0.0/rbgdk-pixbuf2conversions.h
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.0.0/rbgdk.h
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.0.0/rbgdk3.h
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.0.0/rbgdk3conversions.h
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.0.0/rbgdkconversions.h
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.0.0/rbgio2.h
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.0.0/rbgio2conversions.h
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.0.0/rbglib.h
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.0.0/rbglib2conversions.h
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.0.0/rbglibdeprecated.h
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.0.0/rbgobject.h
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.0.0/rbgtk.h
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.0.0/rbgtk3.h
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.0.0/rbgtk3conversions.h
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.0.0/rbgtkconversions.h
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.0.0/rbgtkmacros.h
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.0.0/rbgutil.h
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.0.0/rbgutil_list.h
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.0.0/rbgutildeprecated.h
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.0.0/rbpango.h
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.0.0/rbpangoconversions.h
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.0.0/rbpangoversion.h