time: Fix test failure on AIX 7.2

[Bruno Haible]

Also on AIX 7.2, I see the 'time' test fail. Here too, for ca. 5 milliseconds
after gettimeofday() reports a new second, time(NULL) reports the previous one.

This patch fixes it.


2023-03-17  Bruno Haible  <bruno@clisp.org>

        time: Fix test failure on AIX 7.2.
        * m4/time.m4 (gl_FUNC_TIME): Guess that it does not work on AIX.
        * doc/posix-functions/time.texi: Mention the bug on AIX.

diff --git a/doc/posix-functions/time.texi b/doc/posix-functions/time.texi
index 5d7c719594..c744c63974 100644
--- a/doc/posix-functions/time.texi
+++ b/doc/posix-functions/time.texi
@@ -12,10 +12,10 @@
 This function is not consistent with @code{gettimeofday} and 
@code{timespec_get}
 on some platforms:
 @c https://sourceware.org/bugzilla/show_bug.cgi?id=30200
-glibc 2.31 or newer on Linux, native Windows.
-Namely, in the first 1 to 2.5 milliseconds of every second (or, on Windows,
-in the first 5 milliseconds of every second), @code{time} returns a value
-that is one less than the @code{tv_sec} part of the return value of
+glibc 2.31 or newer on Linux, AIX 7.2, native Windows.
+Namely, in the first 1 to 2.5 milliseconds of every second (or, on AIX and
+Windows, in the first 5 milliseconds of every second), @code{time} returns
+a value that is one less than the @code{tv_sec} part of the return value of
 @code{gettimeofday} or @code{timespec_get}.
 @end itemize
 
diff --git a/m4/time.m4 b/m4/time.m4
index 504ec77f88..4c4e411736 100644
--- a/m4/time.m4
+++ b/m4/time.m4
@@ -1,4 +1,4 @@
-# time.m4 serial 2
+# time.m4 serial 3
 dnl Copyright (C) 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,
@@ -16,6 +16,7 @@ AC_DEFUN([gl_FUNC_TIME]
      dnl   - glibc >= 2.31 with Linux. And binaries produced on glibc < 2.31
      dnl     need to run fine on newer glibc versions as well; therefore ignore
      dnl     __GLIBC_MINOR__.
+     dnl   - AIX,
      dnl   - native Windows.
      case "$host_os" in
        linux*-gnu*)
@@ -30,6 +31,7 @@ AC_DEFUN([gl_FUNC_TIME]
            [gl_cv_func_time_works="guessing no"],
            [gl_cv_func_time_works="guessing yes"])
          ;;
+       aix*)   gl_cv_func_time_works="guessing no";;
        mingw*) gl_cv_func_time_works="guessing no";;
        *) gl_cv_func_time_works="guessing yes";;
      esac