How to force update of OSX app bundle in qmake?

I've written an application that needs access to a large number of resources.

I have a folder on the same level as my .pro file that contains other folders that contain the resources:

Project Directory
  app.pro
  Resources
    ResourceDirA
      ResourceA0.png
      ResourceA1.png
      ...
    ResourceDirB
      ResourceB0.png
      ResourceB1.png
      ...
    ...

In my .pro file, I have the code

macx {
    resources.files = "Resources"
    resources.path = Contents/Resources
    QMAKE_BUNDLE_DATA += resources
}

This works fine when I delete the build directory and rebuild. But when I've already built and I add one file to one of the subdirectories (ResourceA2.png or something) and rebuild, the new file isn't transferred to the app bundle.

Is there a way to ensure that new files are checked for and updated or at least a way to force the entire bundle to be rebuilt every time I build the project?