/usr/lib/petscdir/3.4.2/include/petscconf.h is in libpetsc3.4.2-dev 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/include/../linux-gnu-c-opt/include/petscconf.h