/usr/share/doc/gobjc-mingw-w64-i686 is in gobjc-mingw-w64-i686 5.3.1-8ubuntu3+17.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/gcc-mingw-w64-base
/usr/share/doc/gcc-mingw-w64-base