snprintf: Avoid autoconf warning regarding gl_PRINTF_POSITIONS

[Bruno Haible]

In GNU gettext, autoconf produces this warning:

configure.ac:71: warning: AC_REQUIRE: `gl_PRINTF_POSITIONS' was expanded before 
it was required
configure.ac:71: 
https://www.gnu.org/software/autoconf/manual/autoconf.html#Expanded-Before-Required
gnulib-m4/snprintf-posix.m4:19: gl_FUNC_SNPRINTF_IS_POSIX is expanded from...
gnulib-m4/snprintf-posix.m4:7: gl_FUNC_SNPRINTF_POSIX is expanded from...
gnulib-m4/gnulib-comp.m4:232: lts_INIT is expanded from...

This patch fixes it.


2023-03-30  Bruno Haible  <bruno@clisp.org>

        snprintf: Avoid autoconf warning regarding gl_PRINTF_POSITIONS.
        * m4/printf.m4 (gl_PRINTF_POSITIONS): Define through AC_DEFUN_ONCE.

diff --git a/m4/printf.m4 b/m4/printf.m4
index 7178533a88..cf4e225cfe 100644
--- a/m4/printf.m4
+++ b/m4/printf.m4
@@ -1,4 +1,4 @@
-# printf.m4 serial 79
+# printf.m4 serial 80
 dnl Copyright (C) 2003, 2007-2023 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -1076,7 +1076,7 @@ AC_DEFUN([gl_PRINTF_DIRECTIVE_LC]
 dnl strings with positions. (POSIX:2001)
 dnl Result is gl_cv_func_printf_positions.
 
-AC_DEFUN([gl_PRINTF_POSITIONS],
+AC_DEFUN_ONCE([gl_PRINTF_POSITIONS],
 [
   AC_REQUIRE([AC_PROG_CC])
   AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles