<rmic classname="com.xyz.FooBar" base="${build}/classes"/>runs the rmic compiler for the class com.xyz.FooBar. The compiled files will be stored in the directory ${build}/classes.
<rmic base="${build}/classes" includes="**/Remote*.class"/>runs the rmic compiler for all classes with .class files below ${build}/classes whose classname starts with Remote. The compiled files will be stored in the directory ${build}/classes.