Added ability to name the executable target in schemes.

[elland]

Attempting to address #589. I only managed to gather a small understanding of the code base, so please let me know if there's a simpler/better way of doing this. For example, I don't like that I'm using a value from the build section to configure something in the run section.

It works by adding the executable key to the build subsection of a scheme:

schemes:
  MyScheme:
    build:
      executable: MyExecutable
      targets:
      ...

[BilalReffas]

Good PR we need this 👌 💯

[brentleyjones]

Can you add a changelog entry? Thanks.

[elland]

@brentleyjones ✅

[brentleyjones]

Thanks @elland!

[yonaskolb]

Hi @elland, thanks for the PR! I think this got merged a bit prematurely though. As you say this property makes more sense on run instead of build. Could you please make a new PR for this, and also update the docs at https://github.com/yonaskolb/XcodeGen/blob/master/Docs/ProjectSpec.md#scheme

[brentleyjones]

My bad for not catching that 😬. Thanks @yonaskolb 😄.

[elland]

@yonaskolb yes, but I couldn't really figure out how to do it via run yet. I can try again when I get back to work next week. (It's a 4 day weekend here in Germany)

[yonaskolb]

@elland great thanks! Was there a specific issue you were hitting when adding it to Run? If I'm not mistaken the property should be able to be stored, decoded and read just the same from Build's sibling struct Run instead. But let me know if there's an issue with that 👍

[elland]

@yonaskolb, I think when I tried that I lacked a bit more understanding of the code, I think I'll manage the second time around :)