/usr/include/ is in libc6-dev-i386 2.15-0ubuntu10.18.
This file is owned by root:root, with mode 0o755.
..
/usr/include/sys/
/usr/include/gnu
/usr/include/sys/reg.h
/usr/include/sys/kd.h
/usr/include/sys/errno.h
/usr/include/sys/sysctl.h
/usr/include/sys/ioctl.h
/usr/include/sys/profil.h
/usr/include/sys/fsuid.h
/usr/include/sys/types.h
/usr/include/sys/select.h
/usr/include/sys/uio.h
/usr/include/sys/stropts.h
/usr/include/sys/epoll.h
/usr/include/sys/un.h
/usr/include/sys/timerfd.h
/usr/include/sys/prctl.h
/usr/include/sys/wait.h
/usr/include/sys/file.h
/usr/include/sys/vlimit.h
/usr/include/sys/shm.h
/usr/include/sys/time.h
/usr/include/sys/termios.h
/usr/include/sys/ultrasound.h
/usr/include/sys/vm86.h
/usr/include/sys/elf.h
/usr/include/x86_64-linux-gnu/
/usr/include/x86_64-linux-gnu/gnu/
/usr/include/x86_64-linux-gnu/gnu/stubs-32.h
/usr/include/sys/fanotify.h
/usr/include/sys/statvfs.h
/usr/include/sys/signal.h
/usr/include/sys/timex.h
/usr/include/sys/pci.h
/usr/include/sys/vfs.h
/usr/include/sys/msg.h
/usr/include/sys/swap.h
/usr/include/sys/cdefs.h
/usr/include/sys/acct.h
/usr/include/sys/ustat.h
/usr/include/sys/soundcard.h
/usr/include/sys/mtio.h
/usr/include/sys/vt.h
/usr/include/sys/dir.h
/usr/include/sys/io.h
/usr/include/sys/timeb.h
/usr/include/sys/signalfd.h
/usr/include/sys/syscall.h
/usr/include/sys/sysinfo.h
/usr/include/sys/inotify.h
/usr/include/sys/personality.h
/usr/include/sys/sendfile.h
/usr/include/sys/stat.h
/usr/include/sys/mman.h
/usr/include/sys/klog.h
/usr/include/sys/sem.h
/usr/include/sys/syslog.h
/usr/include/sys/socket.h
/usr/include/sys/raw.h
/usr/include/sys/param.h
/usr/include/sys/gmon_out.h
/usr/include/sys/poll.h
/usr/include/sys/resource.h
/usr/include/sys/ucontext.h
/usr/include/sys/ptrace.h
/usr/include/sys/times.h
/usr/include/sys/ttydefaults.h
/usr/include/sys/utsname.h
/usr/include/sys/ipc.h
/usr/include/sys/user.h
/usr/include/sys/ttychars.h
/usr/include/sys/bitypes.h
/usr/include/sys/fcntl.h
/usr/include/sys/xattr.h
/usr/include/sys/kdaemon.h
/usr/include/sys/mount.h
/usr/include/sys/quota.h
/usr/include/sys/queue.h
/usr/include/sys/gmon.h
/usr/include/sys/statfs.h
/usr/include/sys/sysmacros.h
/usr/include/sys/unistd.h
/usr/include/sys/reboot.h
/usr/include/sys/perm.h
/usr/include/sys/procfs.h
/usr/include/sys/socketvar.h
/usr/include/sys/debugreg.h
/usr/include/sys/vtimes.h
/usr/include/sys/eventfd.h
/usr/include/bits
/usr/include/fpu_control.h