Since version 1.8.2 Ant does not override system properties. For example -Duser.name=newvalue does not override default value as it did before 1.8.2. Other non-system properties can be successfully overridden via -D.
Created attachment 27489 [details] Simple test case demonstrating the problem NB It's not only user.name that's affected, java.home exhibited the same behaviour, so presumably all system properties are the same.
AFAIU this is the side-effect of this change http://svn.apache.org/viewvc/ant/core/trunk/src/main/org/apache/tools/ant/Main.java?r1=948667&r2=954939&diff_format=h
Please fix this.
Thanks for the report, and the pointer to the change that caused this behaviour.