Link and embed all nested Carthage dependencies for macOS

[toshi0383]

Motivation

With spec like this,

targets:
  LGTM:
    platform: macOS
    type: application
    sources: LGTM
    dependencies:
      - target: LGTMKit_macOS
  LGTMKit:
    type: framework
    platform: [iOS, macOS]
    sources: LGTMKit
    dependencies:
      - carthage: APIKit

Generate xcodeproj like this.

Related: #82