/usr/lib/gcc-cross/arm-linux-gnueabihf/6/ecj1 is in gcj-6-arm-linux-gnueabihf 6.3.0-18cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/gcc-cross/arm-linux-gnueabihf/6/../../../x86_64-linux-gnu/gcc/ecj1