/usr/lib/ is in libkf5messagecomposer-dev 4:17.12.3-0ubuntu3.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/x86_64-linux-gnu/
/usr/lib/x86_64-linux-gnu/cmake/
/usr/lib/x86_64-linux-gnu/cmake/KF5MessageComposer/
/usr/lib/x86_64-linux-gnu/cmake/KF5MessageComposer/KF5MessageComposerConfig.cmake
/usr/lib/x86_64-linux-gnu/cmake/KF5MessageComposer/KF5MessageComposerConfigVersion.cmake
/usr/lib/x86_64-linux-gnu/cmake/KF5MessageComposer/KF5MessageComposerTargets-debian.cmake
/usr/lib/x86_64-linux-gnu/cmake/KF5MessageComposer/KF5MessageComposerTargets.cmake
/usr/lib/x86_64-linux-gnu/qt5/
/usr/lib/x86_64-linux-gnu/qt5/mkspecs/
/usr/lib/x86_64-linux-gnu/qt5/mkspecs/modules/
/usr/lib/x86_64-linux-gnu/qt5/mkspecs/modules/qt_MessageComposer.pri
/usr/lib/x86_64-linux-gnu/libKF5MessageComposer.so