Expose CuckooGenerator as executable product

[nmcc24]

Summary

Exposes CuckooGenerator as a public executable product so downstream consumers can build
custom build plugins on top of it. In order to do so, XcodeProj must be bumped to 9.13.0+.

Changes

File	Change
Package.swift	Adds .executable(name: "CuckooGenerator", targets: ["CuckooGenerator"]) product; bumps XcodeProj 9.9.0 → 9.14.0; raises .macOS platform floor 10.15 → 11.0
Package.resolved	Re-resolved pin for XcodeProj → 9.14.0 (eb001108...), originHash regenerated
Generator/Sources/Internal/Helpers/Async+convenience.swift	#available(macOS 14.0, *) → #available(macOS 14.0, iOS 17.0, *) — adds the iOS branch needed now that CuckooGenerator can be built for iOS as a side effect of the executable product

Verification

• swift package resolve — resolves cleanly against the new XcodeProj version.
• swift build — full build succeeds (CuckooGenerator and CuckooGenerator-tool link successfully).

Things to call out to reviewers

• Breaking for consumers still on macOS 10.15: the platform bump to macOS 11.0 is required
  by XcodeProj 9.14.0 itself (its manifest declares 11.0 as its floor), not a choice made here.
  Worth a one-line mention in the PR body since it's a compatibility change, not just a version bump.
• iOS compilation of CuckooGenerator: per the earlier PR discussion, exposing this as an
  executable product means it now also compiles for iOS as a side effect of the platform list,
  even though it's really meant for host-side (macOS) tooling use. Nothing in Package.swift
  stops an app target from linking it. Confirm the README documents that this is intended for
  build-tool/plugin use only, not for shipping inside an app target.
• No behavior changes to existing Cuckoo/mocking runtime code — this is purely packaging +
  dependency surface.

[nmcc24]

In order to ensure successful compilation of CuckooGenerator on the iOS platform, we are currently blocked by tuist/XcodeProj#1016. Once this gets merged, we will be able to finalise compilation of the product.

@MatyasKriz please do let me know if you'd like me to bring any iOS compilation fixes as part of this MR or as a follow up MR.

[MatyasKriz]

I didn't know that you intended to compile the generator for iOS, not sure if that can work, but if you can get it working it's up to you whether to include it in this PR or a follow-up one, I think it shouldn't be an issue either way since most users don't use CuckooGenerator this way.

What I'm a bit hesitant about is that when CuckooGenerator is compilable for iOS, there won't be anything stopping users from using it in their app target instead of the test one, not sure if that happens due to bad README or speeding through without reading it.

[nmcc24]

Hi @MatyasKriz

Thanks for your response and sharing your views.

The compilation for iOS is simply a side effect of running the build tool plugging when targeting that platform.

As far as I have observed, there is no way of restricting a package (and its products) to a particular platform. Even if one does not mentioned them in the Package.swift file, it will end up defaulting to a minimum version.

It is true that by opening up the executable as public product would allow that use case to occur. However, it seems to me that it wouldn't ever work on a platform other than MacOS/Linux. By complementing this with a potential mention on the README file, I believe we would be providing any consumer with enough information - I appreciate however this is very subjective :)

In short, unless we consider modifying the plugin you provide (which I don't think we should consider as it would introduce unnecessary and niche complexity to this repo), I can't see any other way that allows us to enable the composition I'm trying to achieve.

[nmcc24]

@MatyasKriz this is now finally ready to be reviewed as XcodeProj 9.13.0+ now has all necessary changes required to make this happen.

[MatyasKriz]

Looks good, merging. We'll revisit this if users find themselves confused when adding the library.