Fix rpaths

[NQNStudios]

This adds a 1-file submodule which just contains my python script that detects and fixes broken rpath/dependency references in the app bundles. And extends SConstruct to make sure the submodule is cloned, and call the script automatically.

This theoretically would have fixed the problems behind #192 although the script might not cover every possible edge case.

[CelticMinstrel]

1. Can we call it after Xcode builds too?
2. Is there an advantage to making this a submodule rather than just committing the file?

[NQNStudios]

1. I'm not sure how to set that up. I can't get the xcode build to work either.
2. That advantage is on my end -- I'm using it for other things, and I only want to maintain it in one place.

[CelticMinstrel]

I can't get the xcode build to work either.

Oh right, I think you mentioned this before. What was the actual problem with it? Unable to find SFML or something?

[NQNStudios]

Yeah it was something like that. Actually, I might be able to get it to work now using my from-source dependency builds.

[NQNStudios]

I got it working!

[CelticMinstrel]

It seems readlink -f does not work on MacOS 10.15. I also can't find documentation on what it's supposed to do. Can you rewrite your script to use Path.resolve instead?

[NQNStudios]

Yeah