/usr/lib/gap/bin/x86_64-linux-gnu-gcc-default64 is in gap-dev 4r8p8-3.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/gap/bin/../../x86_64-linux-gnu/gap/bin
/usr/lib/gap/bin/../../x86_64-linux-gnu/gap/bin