Emacs 28 on OSX: emacsclient.c:1415: warning: implicit declaration of function 'openat'

[Keith David Bershatsky]

Emacs 28 builds okay on El Capitan, but I am unable to build on OSX 10.6.8 
(with Xcode 3.2.6).  Any suggestions on how to overcome this error in the build 
process would be greatly appreciated.

  AR       libgnu.a
/usr/bin/ranlib: file: libgnu.a(u64.o) has no symbols
/usr/bin/ranlib: file: libgnu.a(unistd.o) has no symbols
ranlib: file: libgnu.a(u64.o) has no symbols
ranlib: file: libgnu.a(unistd.o) has no symbols
/usr/bin/make -C lib-src all
  CCLD     etags
  CCLD     ctags
  CCLD     emacsclient
emacsclient.c: In function 'local_sockname':
emacsclient.c:1415: warning: implicit declaration of function 'openat'
Undefined symbols:
  "_openat", referenced from:
      _local_sockname in ccygiqN2.o
     (maybe you meant: _openat_save_fail, _openat_proc_name , 
_openat_restore_fail )
ld: symbol(s) not found
collect2: ld returned 1 exit status
make[1]: *** [emacsclient] Error 1
make: *** [lib-src] Error 2

Thanks,

Keith