I read it and also looked at the signatures. But it didn't tell me as much as it would have told you. At least it pointed me in the right direction. But I needed more research to get a handle on it. In my case, it was a combination of two problems. In the case of the original recipe, it's just the first one.

- allarch must be last in inherit

  'inherit gnomebase gtk-icon-cache allarch'

- you should not set GTK_IC = "4", as I had previously assumed