Xcode 7 warnings: object file was built for newer iOS version than being linked

I recently integrated Google Cloud Messaging into an app targeting iOS 7 and iOS 8. Just grabbed Xcode 7 beta 4 to get started on iOS 9 support, and now I'm getting an error from the linker:

ld: warning: object file (.../Pods/GoogleInterchangeUtilities/Libraries
/libProtocolBuffers.a(Descriptor.pb.o)) was built for newer iOS version (8.3)
than being linked (7.0)

and a handful more like that all for parts of libProtocolBuffers.a.

Does this mean that iOS 8.3 is required to use the GCM library? If so, why did Xcode 6 happily spit out code that (by all appearances in my testing with iOS 7 devices) delivered push notifications to iOS 7.3 without issue?

Given that they're just warnings, I can still compile fine, however I prefer not to ship code that is wrong.

Edit: I emailed google and they said top people will look into it. In the mean time, if you're reading this and bothered by the warning, maybe also email so they'll be encouraged to deal with it.