/usr/arm-linux-gnueabihf/lib/libgnatprj.so is in libgnatprj5-dev-armhf-cross 5.5.0-12ubuntu1cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/arm-linux-gnueabihf/lib/libgnatprj.so.5
/usr/arm-linux-gnueabihf/lib/libgnatprj.so.5