/usr/include/bullet/ConvexDecomposition/ is in libbullet-extras-dev 2.82-r2704+dfsg-2.
This file is owned by root:root, with mode 0o755.
..
/usr/include/bullet/ConvexDecomposition/ConvexBuilder.h
/usr/include/bullet/ConvexDecomposition/ConvexDecomposition.h
/usr/include/bullet/ConvexDecomposition/bestfit.h
/usr/include/bullet/ConvexDecomposition/bestfitobb.h
/usr/include/bullet/ConvexDecomposition/cd_hull.h
/usr/include/bullet/ConvexDecomposition/cd_vector.h
/usr/include/bullet/ConvexDecomposition/cd_wavefront.h
/usr/include/bullet/ConvexDecomposition/concavity.h
/usr/include/bullet/ConvexDecomposition/fitsphere.h
/usr/include/bullet/ConvexDecomposition/float_math.h
/usr/include/bullet/ConvexDecomposition/meshvolume.h
/usr/include/bullet/ConvexDecomposition/planetri.h
/usr/include/bullet/ConvexDecomposition/raytri.h
/usr/include/bullet/ConvexDecomposition/splitplane.h
/usr/include/bullet/ConvexDecomposition/vlookup.h