Build script should work on sub_build_config in dependencies repos.

[XuefengHuang]

Now, build scripts only work on certain build config. However, installer-packaginghopes that build scripts can refer to sub-build-configs in dependencies repos that also get built in, so that we don’t need to sync dependency updates between the installer-packaging and other dependencies' build scripts. e.g. nodemanager, demokit, repy_v2, seash...

Thus, build scripts need to work on the build_config that we select. After adding this functionality, we also don't need to sync different repos updates.

I think we can add a dependencies (or similar) keyword that we can refer to sub-build-configs in dependencies repos and reuse these build config. For instance, putting these sub_build_configs to one build_config and remove duplicated lines.