[LTP] [PATCH 2/2] configure.ac: Update AC_PROG_AR related comment

[Petr Vorel]

AC_PROG_AR was added much later: in v2.72a [1]. Also it looks like that
redefinition is not a problem thus not wrapping with m4_ifndef([AC_PROG_AR].

NOTE: missing 'ar' don't fail configure (isn't the check useless then?):
$ rm -rf autom4te.cache/; ma autotools && ./configure; echo $?
...
configure:4878: checking for ar
configure:4913: result: no
...
0

[1] https://git.savannah.gnu.org/cgit/autoconf.git/commit/?id=c48fdb81191c8b7c7c0dde6141b861b178a6a284

Signed-off-by: Petr Vorel <pvorel@suse.cz>
---
 configure.ac                    | 3 +--
 testcases/realtime/configure.ac | 3 +--
 2 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/configure.ac b/configure.ac
index c2b0f48e79..edf00687f2 100644
--- a/configure.ac
+++ b/configure.ac
@@ -20,8 +20,7 @@ AM_MAINTAINER_MODE([enable])
 AC_CANONICAL_HOST
 
 AC_PROG_CC
-# <= autoconf 2.61 doesn't have AC_PROG_AR, but 2.63 has it. Not sure about
-# 2.62.
+# autoconf >= v2.72a
 AC_DEFUN([AC_PROG_AR], [AC_CHECK_TOOL(AR, ar, :)])
 AC_PROG_AR
 AC_PROG_RANLIB
diff --git a/testcases/realtime/configure.ac b/testcases/realtime/configure.ac
index 6f50f1490f..39f16f1779 100644
--- a/testcases/realtime/configure.ac
+++ b/testcases/realtime/configure.ac
@@ -12,8 +12,7 @@ AC_CHECK_HEADERS_ONCE([ \
 AC_CANONICAL_HOST
 
 AC_PROG_CC
-# <= autoconf 2.61 doesn't have AC_PROG_AR, but 2.63 has it. Not sure about
-# 2.62.
+# autoconf >= v2.72a
 AC_DEFUN([AC_PROG_AR], [AC_CHECK_TOOL(AR, ar, :)])
 AC_PROG_AR
 AC_PROG_RANLIB
-- 
2.39.0