/usr/lib/petscdir/3.7.7/x86_64-linux-gnu-real-debug/lib/libpetsc_real.so.3.7 is in libpetsc3.7.7-dbg 3.7.7+dfsg1-2build5.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/petscdir/3.7.7/x86_64-linux-gnu-real-debug/lib/libpetsc_real.so.3.7.7