/usr/include/x86_64-linux-gnu/ is in libqt5texttospeech5-dev 5.9.5-0ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/x86_64-linux-gnu/qt5/
/usr/include/x86_64-linux-gnu/qt5/QtTextToSpeech/
/usr/include/x86_64-linux-gnu/qt5/QtTextToSpeech/QTextToSpeech
/usr/include/x86_64-linux-gnu/qt5/QtTextToSpeech/QTextToSpeechEngine
/usr/include/x86_64-linux-gnu/qt5/QtTextToSpeech/QTextToSpeechPlugin
/usr/include/x86_64-linux-gnu/qt5/QtTextToSpeech/QVoice
/usr/include/x86_64-linux-gnu/qt5/QtTextToSpeech/QtTextToSpeech
/usr/include/x86_64-linux-gnu/qt5/QtTextToSpeech/QtTextToSpeechDepends
/usr/include/x86_64-linux-gnu/qt5/QtTextToSpeech/QtTextToSpeechVersion
/usr/include/x86_64-linux-gnu/qt5/QtTextToSpeech/qtexttospeech.h
/usr/include/x86_64-linux-gnu/qt5/QtTextToSpeech/qtexttospeech_global.h
/usr/include/x86_64-linux-gnu/qt5/QtTextToSpeech/qtexttospeechengine.h
/usr/include/x86_64-linux-gnu/qt5/QtTextToSpeech/qtexttospeechplugin.h
/usr/include/x86_64-linux-gnu/qt5/QtTextToSpeech/qttexttospeechversion.h
/usr/include/x86_64-linux-gnu/qt5/QtTextToSpeech/qvoice.h