/usr/lib/gcc-cross/arm-linux-gnueabihf/8/libubsan.so is in libgcc-8-dev-armhf-cross 8-20180414-1ubuntu2cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/gcc-cross/arm-linux-gnueabihf/8/../../../../arm-linux-gnueabihf/lib/libubsan.so.1