lib/dirfd.c: compiler warning: unused parameter

[Bjarni Ingi Gislason]

Software: groff, private repository that is updated regulary with
GNU gnulib.

  with

gnulib_modules="
    git-version-gen
    havelib
    wcwidth
    fprintf-posix
    snprintf
    vsnprintf
    stdint
  setlocale
  vsnprintf-posix
  warnings
  gen-header
  manywarnings
  mkstemp
  fmod
  getcwd
  putenv
  strcase
  strerror
  strtol
  stdckdint
  assert
  assert-h
  idx
  string
  strings
  nullptr
 "

  Changes in "lib/dirfd.c" this year are from commit 3f0950f65ab
(2023-04-27 01:42:25 +0200).

  The compiler reports:

  CC       lib/libgnu_a-dirfd.o
../lib/dirfd.c: In function 'rpl_dirfd':
../lib/dirfd.c:83:13: warning: unused parameter 'dir_p'
[-Wunused-parameter]
   83 | dirfd (DIR *dir_p)
      |        ~~~~~^~~~~
  CC       lib/libgnu_a-dirname-lgpl.o


  From the code, I can't see how the paremeter can not get used while
the code is traversed.