www/subsonic: Fix extract better

There was two issues:

1. Things like USES have to be defined prior to including bsd.options.mk and the like.
2. the UNZIP_CMD is points to the ports unzip which isn't loaded unless USES=zip:infozip (it would have been UNZIP_NATIVE_CMD).

After fixing USES, change UNZIP_CMD to EXTRACT_CMD to fix everywhere.