/usr/ is in ruby-posix-spawn 0.3.11-1build2.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/
/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/posix_spawn_ext.so
/usr/lib/ruby/
/usr/lib/ruby/vendor_ruby/
/usr/lib/ruby/vendor_ruby/posix/
/usr/lib/ruby/vendor_ruby/posix/spawn/
/usr/lib/ruby/vendor_ruby/posix/spawn/child.rb
/usr/lib/ruby/vendor_ruby/posix/spawn/version.rb
/usr/lib/ruby/vendor_ruby/posix/spawn.rb
/usr/lib/ruby/vendor_ruby/posix-spawn.rb
/usr/share/
/usr/share/rubygems-integration/
/usr/share/rubygems-integration/2.3.0/
/usr/share/rubygems-integration/2.3.0/specifications/
/usr/share/rubygems-integration/2.3.0/specifications/posix-spawn-0.3.11.gemspec
/usr/share/doc/
/usr/share/doc/ruby-posix-spawn/
/usr/share/doc/ruby-posix-spawn/examples/
/usr/share/doc/ruby-posix-spawn/examples/posix-spawn-benchmark
/usr/share/doc/ruby-posix-spawn/copyright
/usr/share/doc/ruby-posix-spawn/changelog.Debian.gz
/usr/share/doc/ruby-posix-spawn/README.Debian
/usr/share/doc/ruby-posix-spawn/README.md.gz