[PATCH] Configure: dump unsupported repository error and exit

[Roman Arutyunyan]

# HG changeset patch
# User Roman Arutyunyan <arut at nginx.com>
# Date 1684856745 -14400
#      Tue May 23 19:45:45 2023 +0400
# Branch quic
# Node ID bd25277d0ed77a90766bc2f4153538c86621cdfc
# Parent  a83071314a22652d4a552e72e13d18aa4c01d79e
Configure: dump unsupported repository error and exit.

diff --git a/auto/configure b/auto/configure
--- a/auto/configure
+++ b/auto/configure
@@ -4,6 +4,13 @@
 # Copyright (C) Nginx, Inc.
 
 
+cat << END
+
+$0: this repository is no longer supported, see README
+
+END
+exit 1
+
 LC_ALL=C
 export LC_ALL