/usr/include/x86_64-linux-gnu/ is in libubuntutoolkit5-dev 1.3.1918+16.04.20160404-0ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/x86_64-linux-gnu/qt5/
/usr/include/x86_64-linux-gnu/qt5/UbuntuToolkit/
/usr/include/x86_64-linux-gnu/qt5/UbuntuToolkit/AsyncLoader
/usr/include/x86_64-linux-gnu/qt5/UbuntuToolkit/ColorUtils
/usr/include/x86_64-linux-gnu/qt5/UbuntuToolkit/Tree
/usr/include/x86_64-linux-gnu/qt5/UbuntuToolkit/UbuntuToolkit
/usr/include/x86_64-linux-gnu/qt5/UbuntuToolkit/UbuntuToolkitDepends
/usr/include/x86_64-linux-gnu/qt5/UbuntuToolkit/UbuntuToolkitVersion
/usr/include/x86_64-linux-gnu/qt5/UbuntuToolkit/asyncloader.h
/usr/include/x86_64-linux-gnu/qt5/UbuntuToolkit/colorutils.h
/usr/include/x86_64-linux-gnu/qt5/UbuntuToolkit/tree.h
/usr/include/x86_64-linux-gnu/qt5/UbuntuToolkit/ubuntutoolkitglobal.h
/usr/include/x86_64-linux-gnu/qt5/UbuntuToolkit/ubuntutoolkitversion.h