/usr/lib/petscdir/3.4.2/linux-gnu-cxx-debug is in libpetsc3.4.2-dbg 3.4.2.dfsg1-8.1+b1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/petscdir/3.4.2/linux-gnu-c-debug
/usr/lib/petscdir/3.4.2/linux-gnu-c-debug