/usr/lib/x86_64-linux-gnu/libQt5Xml.so is in qtbase5-dev 5.5.1+dfsg-16ubuntu7.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libQt5Xml.so.5.5.1
/usr/lib/x86_64-linux-gnu/libQt5Xml.so.5.5.1