bit7z: Path Traversal via Null Byte Injection from `gcount()` Off-by-One in `restoreSymlink()`

bit7z is a cross-platform C++ static library that allows the compression/extraction of archive files. Prior to version 4.0.12, a one-byte off-by-one error in SafeOutPathBuilder::restoreSymlink() allows an attacker to craft a .7z archive that, when extracted with bit7z on any non-Windows platform, creates a symlink escaping the intended output directory. Subsequent archive entries extracted through this symlink write arbitrary files outside the extraction directory with the permissions of the extracting process. This issue has been patched in version 4.0.12.