/usr/src/linux-headers-4.15.0-24-lowlatency/arch/ia64 is in linux-headers-4.15.0-24-lowlatency 4.15.0-24.26.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/src/linux-headers-4.15.0-24-lowlatency/arch/../../linux-headers-4.15.0-24/arch/ia64