/usr/include/msgpack/predef/library/ is in libmsgpack-dev 1.4.2-4.
This file is owned by root:root, with mode 0o755.
..
/usr/include/msgpack/predef/library/c/
/usr/include/msgpack/predef/library/c.h
/usr/include/msgpack/predef/library/c/_prefix.h
/usr/include/msgpack/predef/library/c/gnu.h
/usr/include/msgpack/predef/library/c/uc.h
/usr/include/msgpack/predef/library/c/vms.h
/usr/include/msgpack/predef/library/c/zos.h
/usr/include/msgpack/predef/library/std/
/usr/include/msgpack/predef/library/std.h
/usr/include/msgpack/predef/library/std/_prefix.h
/usr/include/msgpack/predef/library/std/cxx.h
/usr/include/msgpack/predef/library/std/dinkumware.h
/usr/include/msgpack/predef/library/std/libcomo.h
/usr/include/msgpack/predef/library/std/modena.h
/usr/include/msgpack/predef/library/std/msl.h
/usr/include/msgpack/predef/library/std/roguewave.h
/usr/include/msgpack/predef/library/std/sgi.h
/usr/include/msgpack/predef/library/std/stdcpp3.h
/usr/include/msgpack/predef/library/std/stlport.h
/usr/include/msgpack/predef/library/std/vacpp.h