[Perl/perl5] b7ed27: only define ingroup() where needed (i.e. on !DOSIS...

[mauke via perl5-changes]

  Branch: refs/heads/blead
  Home:   https://github.com/Perl/perl5
  Commit: b7ed279824f39feb87bb9704af63f009125b974c
      
https://github.com/Perl/perl5/commit/b7ed279824f39feb87bb9704af63f009125b974c
  Author: Lukas Mai <lukasmai....@gmail.com>
  Date:   2024-02-03 (Sat, 03 Feb 2024)

  Changed paths:
    M doio.c
    M embed.fnc
    M embed.h
    M proto.h

  Log Message:
  -----------
  only define ingroup() where needed (i.e. on !DOSISH systems)

This avoids a compiler warning on MinGW systems:

    ..\doio.c: At top level:
    ..\doio.c:3002:1: warning: 'S_ingroup' defined but not used 
[-Wunused-function]
     3002 | S_ingroup(pTHX_ Gid_t testgid, bool effective)
          | ^~~~~~~~~

See issue #21916.