/usr/include/bullet/BulletCollision/NarrowPhaseCollision/ is in libbullet-dev 2.82-r2704+dfsg-2.
This file is owned by root:root, with mode 0o755.
..
/usr/include/bullet/BulletCollision/NarrowPhaseCollision/btContinuousConvexCollision.h
/usr/include/bullet/BulletCollision/NarrowPhaseCollision/btConvexCast.h
/usr/include/bullet/BulletCollision/NarrowPhaseCollision/btConvexPenetrationDepthSolver.h
/usr/include/bullet/BulletCollision/NarrowPhaseCollision/btDiscreteCollisionDetectorInterface.h
/usr/include/bullet/BulletCollision/NarrowPhaseCollision/btGjkConvexCast.h
/usr/include/bullet/BulletCollision/NarrowPhaseCollision/btGjkEpa2.h
/usr/include/bullet/BulletCollision/NarrowPhaseCollision/btGjkEpaPenetrationDepthSolver.h
/usr/include/bullet/BulletCollision/NarrowPhaseCollision/btGjkPairDetector.h
/usr/include/bullet/BulletCollision/NarrowPhaseCollision/btManifoldPoint.h
/usr/include/bullet/BulletCollision/NarrowPhaseCollision/btMinkowskiPenetrationDepthSolver.h
/usr/include/bullet/BulletCollision/NarrowPhaseCollision/btPersistentManifold.h
/usr/include/bullet/BulletCollision/NarrowPhaseCollision/btPointCollector.h
/usr/include/bullet/BulletCollision/NarrowPhaseCollision/btPolyhedralContactClipping.h
/usr/include/bullet/BulletCollision/NarrowPhaseCollision/btRaycastCallback.h
/usr/include/bullet/BulletCollision/NarrowPhaseCollision/btSimplexSolverInterface.h
/usr/include/bullet/BulletCollision/NarrowPhaseCollision/btSubSimplexConvexCast.h
/usr/include/bullet/BulletCollision/NarrowPhaseCollision/btVoronoiSimplexSolver.h