Re-enabling --packages flag which allows user to crossgen dependencies

* Re-enabling --packages flag which allows user to crossgen dependencies

* In rare case where there is circular dependency between packages, crossgen would not terminate with error but try its best to continue and treats it circular dependent as missing dependency

* LocalPackage class should also ignore native images
This logic isn't right. It will crossgen *everything* which is wrong. We need to properly design this feature and make it more robust (especially since we have the global package repository).