/usr/lib/gcc-cross/mipsel-linux-gnu/6/n32/libgfortran.so is in libn32gfortran-6-dev-mipsel-cross 6.4.0-17ubuntu1cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/gcc-cross/mipsel-linux-gnu/6/n32/../../../../../mipsel-linux-gnu/lib32/libgfortran.so.3