build: consolidate smack avoidance to --without-libsmack

configure accepted (and needed) both --without-libsmack
and --disable-libsmack specified, to fully disable support.

* gl/modules/smack: Require gl_FUNC_ACL_ARG so we
use a consistent and single --without-libsmack option.
This also better aligns with --without-selinux.
* NEWS: Mention the Build-related change.

NEWS

@@ -90,6 +90,9 @@ GNU coreutils NEWS                                    -*- outline -*-
   gzip-compressed tarballs are no longer distributed,
   instead being replaced with zstandard-compressed tarballs.
 
+  The configure option '--disable-libsmack' is consolidated to
+  '--without-libsmack'.  The option '--disable-libsmack' is now deprecated.
+
 
 * Noteworthy changes in release 9.12 (2026-09-14) [stable]
 

gl/modules/smack

@@ -3,15 +3,15 @@ Include and determine the availability of smack routines
 
 Files:
 lib/smack.h
+m4/acl.m4
 
 Depends-on:
 
 configure.ac:
 # Check whether libsmack is available
 LIB_SMACK=
-AC_ARG_ENABLE([libsmack],
-  AS_HELP_STRING([--disable-libsmack], [disable libsmack support]))
-if test "X$enable_libsmack" != "Xno"; then
+AC_REQUIRE([gl_FUNC_ACL_ARG])
+if test "X$with_libsmack" != "Xno"; then
   AC_CHECK_LIB([smack], [smack_new_label_from_self],
     [AC_CHECK_LIB([smack], [smack_new_label_from_path],
       [AC_CHECK_HEADER([sys/smack.h],
@@ -19,7 +19,7 @@ if test "X$enable_libsmack" != "Xno"; then
          AC_DEFINE([HAVE_SMACK], [1], [libsmack usability])]
       )])])
   if test "X$LIB_SMACK" = "X"; then
-    if test "X$enable_libsmack" = "Xyes"; then
+    if test "X$with_libsmack" = "Xyes"; then
       AC_MSG_ERROR([libsmack library was not found or not usable])
     fi
   fi