/usr/lib/x86_64-linux-gnu/qt-default/qtchooser/default.conf is in libqtcore4 4:4.8.7+dfsg-5ubuntu2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/qt-default/qtchooser/../../../../share/qtchooser/qt4-x86_64-linux-gnu.conf