AFAIK nothing in juce actually directly includes CoreImage. If it's being indirectly included by another framework, then I really don't know why, and haven't seen this ourselves in Xcode 7
This is just because you're building for a different target OS than the one you're running on. For some reason Xcode by default on 10.10 will build apps that only run on 10.11 (doh!) so you need to explicitly dial it back to be 10.10 compatible (or earlier).
But you don't need to use an earlier SDK, you only need to change the "deployment target". You can do that in the Introjucer or Xcode.
Update: Properly setting the deployment target indeed fixes this.
In my case one of the compilation targets had a different setting that I wasn’t aware of, because I never set targets manually (use global xcconfig files). So I shot myself in the foot here. I’m sorry for the noise!