asconfigc: Does not properly unpack ANEs containing symbolic links

I received the following error when trying to debug a project that made use of an ANE on macOS:

> ArgumentError: Error #3500: The extension context does not have a method with the name SomeNativeMethod.

The ANE contains a native macOS framework, which makes use of symbolic links (e.g. `MyNativeExtension -> Versions/Current/MyNativeExtension`).

I found that asconfigc's `unpackANE` method does not handle the creation of symbolic links and instead writes the links out as text files, leading to the extension not being loaded.

I've created a potential fix; I will submit and link the pull request.

Start at asconfigc's unpackANE method and inspect how entries in an ANE are extracted on macOS. Verify the behavior against an ANE containing symbolic links, and consider the issue resolved when those links remain symbolic links rather than being written as text files so the native extension can load.

Written by the indexing model from the issue text.