mport directory asset installation is vulnerable to symlink and path traversal races

mport is the MidnightBSD Package Manager. Prior to 2.7.8, directory assets handled as ASSET_DIR or ASSET_DIR_OWNER_MODE in libmport/bundle_read_install_pkg.c used path-based mport_mkdirp(), ownership, and permission operations. A local attacker able to modify part of the target installation tree could use dot-dot traversal or substitute symlinks during privileged package installation, causing directory creation or attribute changes to affect attacker-selected paths outside the intended package directories. This issue is fixed in version 2.7.8.