Mk/Uses/java.mk: Runtime fix with USES=java:ant

USES=java:ant does not imply USES=java:run so we need to add the run arg
seperately when we are using USES=java:ant. Not all ports require the
the argument so it is better to address the ports individually instead
of handling it automatically by implying run for ant.

Thanks to vvd for carefully going through this.

Reported by: vvd
Approved by: portmgr (blanket)