/usr/ is in libopenthreads-dev 3.2.3+dfsg1-2ubuntu8.
This file is owned by root:root, with mode 0o755.
..
/usr/include/
/usr/include/OpenThreads/
/usr/include/OpenThreads/Atomic
/usr/include/OpenThreads/Barrier
/usr/include/OpenThreads/Block
/usr/include/OpenThreads/Condition
/usr/include/OpenThreads/Config
/usr/include/OpenThreads/Exports
/usr/include/OpenThreads/Mutex
/usr/include/OpenThreads/ReadWriteMutex
/usr/include/OpenThreads/ReentrantMutex
/usr/include/OpenThreads/ScopedLock
/usr/include/OpenThreads/Thread
/usr/include/OpenThreads/Version
/usr/lib/
/usr/lib/x86_64-linux-gnu/
/usr/lib/x86_64-linux-gnu/pkgconfig/
/usr/lib/x86_64-linux-gnu/pkgconfig/openthreads.pc
/usr/share/
/usr/share/doc/
/usr/share/doc/libopenthreads-dev/
/usr/share/doc/libopenthreads-dev/copyright
/usr/lib/x86_64-linux-gnu/libOpenThreads.so
/usr/share/doc/libopenthreads-dev/changelog.Debian.gz