/usr/include/bullet/Bullet3OpenCL/RigidBody/kernels/ is in libbullet-dev 2.87+dfsg-2.
This file is owned by root:root, with mode 0o755.
..
/usr/include/bullet/Bullet3OpenCL/RigidBody/kernels/batchingKernels.h
/usr/include/bullet/Bullet3OpenCL/RigidBody/kernels/batchingKernelsNew.h
/usr/include/bullet/Bullet3OpenCL/RigidBody/kernels/integrateKernel.h
/usr/include/bullet/Bullet3OpenCL/RigidBody/kernels/jointSolver.h
/usr/include/bullet/Bullet3OpenCL/RigidBody/kernels/solveContact.h
/usr/include/bullet/Bullet3OpenCL/RigidBody/kernels/solveFriction.h
/usr/include/bullet/Bullet3OpenCL/RigidBody/kernels/solverSetup.h
/usr/include/bullet/Bullet3OpenCL/RigidBody/kernels/solverSetup2.h
/usr/include/bullet/Bullet3OpenCL/RigidBody/kernels/solverUtils.h
/usr/include/bullet/Bullet3OpenCL/RigidBody/kernels/updateAabbsKernel.h