Add comment explaining -iquote vs -I and discovery of external deps
Add comment explaining -iquote vs -I and discovery of external deps

sschiau/swift-package-manager,JGiola/swift-package-manager,sschiau/swift-package-manager,apple/swift-package-manager,apple/swift-package-manager,mxcl/swift-package-manager,haskellswift/swift-package-manager,haskellswift/swift-package-manager,abertelrud/swift-package-manager,mxcl/swift-package-manager,abertelrud/swift-package-manager,sschiau/swift-package-manager,sschiau/swift-package-manager,JGiola/swift-package-manager,vmanot/swift-package-manager,vmanot/swift-package-manager,haskellswift/swift-package-manager,apple/swift-package-manager,sschiau/swift-package-manager,abertelrud/swift-package-manager,vmanot/swift-package-manager,mxcl/swift-package-manager,vmanot/swift-package-manager,JGiola/swift-package-manager,abertelrud/swift-package-manager,apple/swift-package-manager,JGiola/swift-package-manager,abertelrud/swift-package-manager,apple/swift-package-manager,JGiola/swift-package-manager,haskellswift/swift-package-manager,vmanot/swift-package-manager,mxcl/swift-package-manager