Handle duplicate dependencies with same/different version in post-install

[victorb]

Currently, we just symlink the package from the node_modules/gx/:hash directory, but what if we have duplicate dependencies that are using different versions? Then we'll use a random one, which is not good enough

[Gozala]

You could link them not at the top package, but rather at the local level, in fact that would have another benefit of making pachake that isn’t listed as dependency available which may happen in current setup