/usr/mips64-linux-gnuabi64/lib/libgfortran.so.3 is in libgfortran3-mips64-cross 5.3.1-14ubuntu2cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/mips64-linux-gnuabi64/lib/libgfortran.so.3.0.0