/usr/lib/gcc-cross/mips64-linux-gnuabi64/5/ecj1 is in gcj-5-mips64-linux-gnuabi64 5.3.1-14ubuntu2cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/gcc-cross/mips64-linux-gnuabi64/5/../../../gcc/x86_64-linux-gnu/5/ecj1