configure.ac: adjust to native inotify support for FreeBSD 15+

FreeBSD 15 has native inotify support, and no "libinotify.pc" pkg config
file anymore, plus no extra includes are needed.  This works fine if we
conditionalize the FreeBSD check to "freebsd-1[0-4]".

Due to m4 involvement double braces are needed for quoting.

See https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=293176

Reported-by: Ivo Karabojkov <karabojkov@kit.bg>
Reported-by: Marek Zarychta <zarychtam@plan-b.pwste.edu.pl>

Change-Id: Ie3f209a641c2f56494dfc7720b13f2a2ba3001a8
Signed-off-by: Gert Doering <gert@greenie.muc.de>
Acked-by: Antonio Quartulli <antonio@mandelbit.com>
Gerrit URL: https://gerrit.openvpn.net/c/openvpn/+/1535
Message-Id: <20260220102106.32024-1-gert@greenie.muc.de>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg35761.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>
(cherry picked from commit 38243844f2)

configure.ac

@@ -1447,7 +1447,7 @@ fi
 
 if test "${enable_async_push}" = "yes"; then
 	case "$host" in
-		*-*-freebsd*)
+		*-*-freebsd1[[0-4]]*)
 			PKG_CHECK_MODULES(
 				[OPTIONAL_INOTIFY],
 				[libinotify],