Java 9 compilation support (#1786)

Author: ahornace

build.xml

@@ -151,7 +151,10 @@ Copyright (c) 2005, 2017, Oracle and/or its affiliates. All rights reserved.
 
     <target name="get-java-version">
         <condition property="java.version.checked">
-            <equals arg1="${ant.java.version}" arg2="1.8"/>
+            <or>
+                <equals arg1="${ant.java.version}" arg2="1.8"/>
+                <equals arg1="${ant.java.version}" arg2="9"/>
+            </or>
         </condition>
     </target>