/usr/src/linux-headers-4.15.0-1024-gcp/scripts/Makefile.clean is in linux-headers-4.15.0-1024-gcp 4.15.0-1024.25~16.04.2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/src/linux-headers-4.15.0-1024-gcp/scripts/../../linux-gcp-headers-4.15.0-1024/scripts/Makefile.clean