/usr/lib/ is in ruby-qt4 4:4.14.3-1ubuntu2.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/x86_64-linux-gnu/
/usr/lib/x86_64-linux-gnu/ruby/
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.3.0/
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.3.0/qtruby4.so
/usr/lib/ruby/
/usr/lib/ruby/vendor_ruby/
/usr/lib/ruby/vendor_ruby/2.3.0/
/usr/lib/ruby/vendor_ruby/2.3.0/Qt.rb
/usr/lib/ruby/vendor_ruby/2.3.0/Qt4.rb
/usr/lib/ruby/vendor_ruby/2.3.0/Qt3.rb
/usr/lib/ruby/vendor_ruby/2.3.0/Qt/
/usr/lib/ruby/vendor_ruby/2.3.0/Qt/active_item_model.rb
/usr/lib/ruby/vendor_ruby/2.3.0/Qt/qtruby4.rb
/usr/lib/ruby/vendor_ruby/2.3.0/Qt/active_table_model.rb