/usr/lib/x86_64-linux-gnu/pkgconfig/libgcj15.pc is in libgcj15-dev 4.9.3-13ubuntu2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/pkgconfig/libgcj-4.9.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libgcj-4.9.pc