/usr/x86_64-linux-gnux32/lib/libobjc.so.4 is in libobjc4-x32-cross 8-20180414-1ubuntu2cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/x86_64-linux-gnux32/lib/libobjc.so.4.0.0
/usr/x86_64-linux-gnux32/lib/libobjc.so.4.0.0