/usr/lib/gcc/x86_64-linux-gnu/5/include/d/core/sys/linux/ is in libphobos-5-dev 5.5.0-12ubuntu1.
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..
/usr/lib/gcc/x86_64-linux-gnu/5/include/d/core/sys/linux/config.d
/usr/lib/gcc/x86_64-linux-gnu/5/include/d/core/sys/linux/dlfcn.d
/usr/lib/gcc/x86_64-linux-gnu/5/include/d/core/sys/linux/elf.d
/usr/lib/gcc/x86_64-linux-gnu/5/include/d/core/sys/linux/epoll.d
/usr/lib/gcc/x86_64-linux-gnu/5/include/d/core/sys/linux/errno.d
/usr/lib/gcc/x86_64-linux-gnu/5/include/d/core/sys/linux/execinfo.d
/usr/lib/gcc/x86_64-linux-gnu/5/include/d/core/sys/linux/link.d
/usr/lib/gcc/x86_64-linux-gnu/5/include/d/core/sys/linux/stdio.d
/usr/lib/gcc/x86_64-linux-gnu/5/include/d/core/sys/linux/sys/
/usr/lib/gcc/x86_64-linux-gnu/5/include/d/core/sys/linux/sys/inotify.d
/usr/lib/gcc/x86_64-linux-gnu/5/include/d/core/sys/linux/sys/mman.d
/usr/lib/gcc/x86_64-linux-gnu/5/include/d/core/sys/linux/sys/signalfd.d
/usr/lib/gcc/x86_64-linux-gnu/5/include/d/core/sys/linux/sys/sysinfo.d
/usr/lib/gcc/x86_64-linux-gnu/5/include/d/core/sys/linux/sys/xattr.d
/usr/lib/gcc/x86_64-linux-gnu/5/include/d/core/sys/linux/termios.d
/usr/lib/gcc/x86_64-linux-gnu/5/include/d/core/sys/linux/time.d
/usr/lib/gcc/x86_64-linux-gnu/5/include/d/core/sys/linux/tipc.d