SECURITY UPDATE: uncontrolled recursion (stack-overflow DoS) in
phar_get_link_source() on circular symlink chains in tar/phar archives
debian/patches/CVE-2026-7260.patch: replace the recursive
phar_get_link_source() with Floyd cycle detection in ext/phar/util.c,
and restore the phar path separator in phar_get_link_location() so the
symlink walk stays idempotent