Cloned the repo afresh and here's the error
/Users/a/Documents/flutterplugins/packages/google_maps_flutter/example/ios/Pods/Headers/Public/GoogleMaps/GoogleMaps/GMSAddress.h:14:9: Module 'GoogleMapsBase' not found

Seemingly fixed by manually adding this path to framework search paths (target google_maps_flutter):
/Users/a/Documents/flutterplugins/packages/google_maps_flutter/example/ios/Pods/GoogleMaps/Base/Frameworks

But since it does not show up in git it must be an ignored file somewhere.