Firebase Undefined symbols for architecture x86_64

Question

I am using firebase as part of a project I am working on in iOS, and I just stumbled upon the following linking error when I try to compile my code against an iPhone 6 or 7

Answer 1

Just discovered a similar problem and got it solved by clearing Pod-Cache.

Clear CocoaPods Cache

pod deintegrate && pod cache clean --all

Re-Install Pods

pod install