$NetBSD: patch-configure,v 1.2 2018/07/27 07:51:30 jperkin Exp $

dirfd is a function not a declaration.

--- configure.orig	2018-06-08 01:06:39.000000000 +0000
+++ configure
@@ -2182,6 +2182,8 @@ $as_echo "#define _DARWIN_C_SOURCE 1" >>
 
 define_xopen_source=yes
 
+ac_sys_system=`uname -s`
+ac_sys_release=`uname -r`
 # Some systems cannot stand _XOPEN_SOURCE being defined at all; they
 # disable features if it is defined, without any means to access these
 # features as extensions. For these systems, we skip the definition of
@@ -3662,10 +3664,10 @@ _ACEOF
 fi
 done
 
-ac_fn_c_check_decl "$LINENO" "dirfd" "ac_cv_have_decl_dirfd" "#include <sys/types.h>
+ac_fn_c_check_func "$LINENO" "dirfd" "ac_cv_have_func_dirfd" "#include <sys/types.h>
        #include <dirent.h>
 "
-if test "x$ac_cv_have_decl_dirfd" = xyes; then :
+if test "x$ac_cv_have_func_dirfd" = xyes; then :
 
 $as_echo "#define HAVE_DIRFD 1" >>confdefs.h