/usr/aarch64-linux-gnu/lib/libatomic.so.1 is in libatomic1-arm64-cross 6.3.0-18cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/aarch64-linux-gnu/lib/libatomic.so.1.2.0
/usr/aarch64-linux-gnu/lib/libatomic.so.1.2.0