/usr/include/postgres-xc/server/pgxc/ is in postgres-xc-server-dev 1.1-2ubuntu2.
This file is owned by root:root, with mode 0o755.
..
/usr/include/postgres-xc/server/pgxc/barrier.h
/usr/include/postgres-xc/server/pgxc/copyops.h
/usr/include/postgres-xc/server/pgxc/execRemote.h
/usr/include/postgres-xc/server/pgxc/groupmgr.h
/usr/include/postgres-xc/server/pgxc/locator.h
/usr/include/postgres-xc/server/pgxc/nodemgr.h
/usr/include/postgres-xc/server/pgxc/pgxc.h
/usr/include/postgres-xc/server/pgxc/pgxcnode.h
/usr/include/postgres-xc/server/pgxc/poolcomm.h
/usr/include/postgres-xc/server/pgxc/poolmgr.h
/usr/include/postgres-xc/server/pgxc/poolutils.h
/usr/include/postgres-xc/server/pgxc/redistrib.h
/usr/include/postgres-xc/server/pgxc/remotecopy.h
/usr/include/postgres-xc/server/pgxc/xc_maintenance_mode.h