I do not like the current process of marking incompatibility, as it is a dog to use from programmatic task access. We should validate immediatly before execution instead. This commit is not a fix, merely a partial workaround.

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@276261 13f79535-47bb-0310-9956-ffa450edef68

src/main/org/apache/tools/ant/taskdefs/Java.java

@@ -578,7 +578,7 @@ public class Java extends Task {
      */
     public void setTimeout(Long value) {
         timeout = value;
-        incompatibleWithSpawn = true;
+        incompatibleWithSpawn |= timeout!=null;
     }
 
     /**