6711276: langtools has incorrect -Werror switch

Reviewed-by: ksrini

make/build.properties

 #
-# Copyright 2007 Sun Microsystems, Inc.  All Rights Reserved.
+# Copyright 2007-2008 Sun Microsystems, Inc.  All Rights Reserved.
 # DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 #
 # This code is free software; you can redistribute it and/or modify it
@@ -66,7 +66,7 @@ javac.no.jdk.warnings = -XDignore.symbol.file=true
 # set the following to -version to verify the versions of javac being used
 javac.version.opt = 
 # in time, there should be no exceptions to -Xlint:all
-javac.lint.opts = -Xlint:all,-deprecation,-fallthrough,-serial -Werror
+javac.lint.opts = -Xlint:all,-deprecation,-fallthrough,-serial,-unchecked,-cast
 
 # options for the <javadoc> task for javac
 javadoc.jls3.url=http://java.sun.com/docs/books/jls/