/usr/include/postgres-xc/server/port/ is in postgres-xc-server-dev 1.1-2ubuntu2.
This file is owned by root:root, with mode 0o755.
..
/usr/include/postgres-xc/server/port/aix.h
/usr/include/postgres-xc/server/port/cygwin.h
/usr/include/postgres-xc/server/port/darwin.h
/usr/include/postgres-xc/server/port/freebsd.h
/usr/include/postgres-xc/server/port/hpux.h
/usr/include/postgres-xc/server/port/irix.h
/usr/include/postgres-xc/server/port/linux.h
/usr/include/postgres-xc/server/port/netbsd.h
/usr/include/postgres-xc/server/port/openbsd.h
/usr/include/postgres-xc/server/port/osf.h
/usr/include/postgres-xc/server/port/sco.h
/usr/include/postgres-xc/server/port/solaris.h
/usr/include/postgres-xc/server/port/unixware.h
/usr/include/postgres-xc/server/port/win32/
/usr/include/postgres-xc/server/port/win32.h
/usr/include/postgres-xc/server/port/win32/arpa/
/usr/include/postgres-xc/server/port/win32/arpa/inet.h
/usr/include/postgres-xc/server/port/win32/dlfcn.h
/usr/include/postgres-xc/server/port/win32/grp.h
/usr/include/postgres-xc/server/port/win32/netdb.h
/usr/include/postgres-xc/server/port/win32/netinet/
/usr/include/postgres-xc/server/port/win32/netinet/in.h
/usr/include/postgres-xc/server/port/win32/pwd.h
/usr/include/postgres-xc/server/port/win32/sys/
/usr/include/postgres-xc/server/port/win32/sys/socket.h
/usr/include/postgres-xc/server/port/win32/sys/wait.h
/usr/include/postgres-xc/server/port/win32_msvc/
/usr/include/postgres-xc/server/port/win32_msvc/dirent.h
/usr/include/postgres-xc/server/port/win32_msvc/sys/
/usr/include/postgres-xc/server/port/win32_msvc/sys/file.h
/usr/include/postgres-xc/server/port/win32_msvc/sys/param.h
/usr/include/postgres-xc/server/port/win32_msvc/sys/time.h
/usr/include/postgres-xc/server/port/win32_msvc/unistd.h
/usr/include/postgres-xc/server/port/win32_msvc/utime.h
/usr/include/postgres-xc/server/portability/instr_time.h