Ensure that buildconf.bat does nothing unless it is used with a CVS checkout.

buildconf.bat

@@ -1,8 +1,21 @@
 @echo off
-REM set up a CVS tree to build when there's no autotools
-REM $Revision$
-REM $Date$
+REM
+REM $Id$
+REM
+REM This batch file must be used to set up a CVS tree to build on
+REM systems where there is no autotools support (i.e. Microsoft).
+REM
+REM This file is not included nor needed for c-ares' release
+REM archives, neither for c-ares' daily snapshot archives.
 
-REM create ares_build.h
+if exist CVS-INFO goto start_doing
+ECHO ERROR: This file shall only be used with a c-ares CVS tree checkout.
+goto end_all
+:start_doing
+
+if not exist ares_build.h.dist goto end_ares_build_h
 copy /Y ares_build.h.dist ares_build.h
+:end_ares_build_h
+
+:end_all