/usr/lib/x86_64-linux-gnu/pkgconfig/libgcj.pc is in gcj-jdk 4:4.9.2-2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/pkgconfig/libgcj15.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libgcj15.pc