autoconf: doc: update ‘find’ info

https://github.com/libsdl-org/autoconf/commit/407d5955f06523d464f40c118d326de3cf1ee3b9

From 407d5955f06523d464f40c118d326de3cf1ee3b9 Mon Sep 17 00:00:00 2001
From: Paul Eggert <[EMAIL REDACTED]>
Date: Sat, 9 Oct 2021 18:38:25 -0700
Subject: [PATCH] =?UTF-8?q?doc:=20update=20=E2=80=98find=E2=80=99=20info?=
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* doc/autoconf.texi (Limitations of Usual Tools):
Mention a few more GNU ‘find’ options that are not portable.
Modernize a bit.
---
 doc/autoconf.texi | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/doc/autoconf.texi b/doc/autoconf.texi
index db736c7f..17a6326e 100644
--- a/doc/autoconf.texi
+++ b/doc/autoconf.texi
@@ -19500,13 +19500,17 @@ Tru64/OSF 5.1 @command{fgrep} does not match an empty pattern.
 @item @command{find}
 @c -----------------
 @prindex @command{find}
-The @option{-maxdepth} option seems to be GNU specific.
-Tru64 v5.1, NetBSD 1.5 and Solaris @command{find}
-commands do not understand it.
+Many operands of GNU @command{find} are not standardized by Posix and
+are missing on many platforms. These nonportable operands include
+@option{-follow}, @option{-maxdepth}, @option{-mindepth},
+@option{-printf}, and @option{,}.  See the
+@uref{https://@/pubs.opengroup.org/@/onlinepubs/@/9699919799/@/utilities/@/find.html,
+Posix spec for @command{find}} for @command{find} operands that
+should be portable nowadays.
 
 The replacement of @samp{@{@}} is guaranteed only if the argument is
 exactly @emph{@{@}}, not if it's only a part of an argument.  For
-instance on DU, and HP-UX 10.20 and HP-UX 11:
+instance, on HP-UX 11:
 
 @example
 $ @kbd{touch foo}
@@ -19516,6 +19520,7 @@ $ @kbd{find . -name foo -exec echo "@{@}-@{@}" \;}
 
 @noindent
 while GNU @command{find} reports @samp{./foo-./foo}.
+Posix allows either behavior.
 
 
 @anchor{grep}