Create an OS release file for compatibility:

touch /etc/lfs-release

Prepare the kernel to build external modules:

cd /usr/src/linux
make mrproper
cp /boot/config-4.8.13 .config
make prepare
make scripts
ln -s ../generated/uapi/linux/version.h include/linux/version.h

Get the install script from the VBox Additions cdrom:

mount -o ro /dev/sr0 /mnt
rsync -acvhP /mnt/VBoxLinuxAdditions.run /tmp
umount /mnt

Run the install script:

cd /tmp
./VBoxLinuxAdditions.run

Cleanup:

rm /etc/lfs-release /tmp/VBoxLinuxAdditions.run

Restart xdm:

systemctl restart xdm

After login, run the VirtualBox clients:

VBoxClient-all