Bug 319352 – [CMake] Fix build against recent internal SDKs

• Status: RESOLVED
• Resolution: FIXED
• Component: CMake

[zak ridouh]

Four independent build breaks surface when building the Mac CMake port
against the internal macOS 27 SDK, where WebKitAdditions turns on feature
flags that the CMake build wasn't fully wired up for:

- OptionsCocoa.cmake: the empty AppleFeatures.h stub was placed on -isystem
  for internal-SDK builds too, shadowing the SDK's real header and tripping
  #warning-as-error in MediaExperience's MXFeatureFlags.h. Guard the stub with
  NOT USE_APPLE_INTERNAL_SDK, matching the sibling availability-overlay block.

- Headers.cmake: add GPUProcess/graphics/Model/ModelTypes.h to
  WebKit_PROJECT_HEADERS so <WebKit/ModelTypes.h> resolves via the header map,
  alongside its already-listed siblings Float3.h and Float4x4.h.

- CMakeLists.txt: expose TextGranularity.h through the WebCore_Private Swift
  module map so WKTextSelectionController.swift can name WebCore.TextGranularity.

- PlatformMac.cmake: add the companion Swift files of the AppKit-gestures unit
  (WebPageProxy.swift, Logger+Extras.swift, WKAppKitGestureController.swift,
  IntRectCG.swift, FloatRectCG.swift). WKTextSelectionController.swift was added
  without them, so the WebKit.swiftmodule emit-module failed on missing members.

[Radar WebKit Bug Importer]

<rdar://problem/182164452>

[zak ridouh]

Pull request: https://github.com/WebKit/WebKit/pull/69346

[EWS]

Committed 317128@main (4bcd765a466a): <https://commits.webkit.org/317128@main>

Reviewed commits have been landed. Closing PR #69346 and removing active labels.