Fix native framework relative path calculation

[jasssonpet]

Previously when adding a framework to the Xcode project the path was wrongly calculated when --path is used:

The correct one should be:

CFC86276F86A4C9B9A1EC768 /* TNSWidgets.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = TNSWidgets.framework; path = "$(SRCROOT)/../../node_modules/tns-core-modules-widgets/platforms/ios/TNSWidgets.framework"; sourceTree = "<group>"; };