/usr/include/directfb/direct/os/ is in libdirectfb-dev 1.7.7-8.
This file is owned by root:root, with mode 0o755.
..
/usr/include/directfb/direct/os/clock.h
/usr/include/directfb/direct/os/filesystem.h
/usr/include/directfb/direct/os/linux/
/usr/include/directfb/direct/os/linux/glibc/
/usr/include/directfb/direct/os/linux/glibc/filesystem.h
/usr/include/directfb/direct/os/linux/glibc/mutex.h
/usr/include/directfb/direct/os/linux/glibc/thread.h
/usr/include/directfb/direct/os/linux/glibc/types.h
/usr/include/directfb/direct/os/linux/glibc/waitqueue.h
/usr/include/directfb/direct/os/log.h
/usr/include/directfb/direct/os/mem.h
/usr/include/directfb/direct/os/mutex.h
/usr/include/directfb/direct/os/signals.h
/usr/include/directfb/direct/os/system.h
/usr/include/directfb/direct/os/thread.h
/usr/include/directfb/direct/os/types.h
/usr/include/directfb/direct/os/waitqueue.h