DeveloperSetupGuide.md protobuf version required.
DeveloperSetupGuide.md protobuf version required.

A dependency on 'protobuf/implicit_weak_message.cc' was added on PR 441e20999427f0af9f1aabb35ac98682bdd7c49f. This file only exists on protobuf version 3.6.0 and higher and user older versions (which used to work before) now causes a build break.
This pull request updates the guide to specify the new requirement.
google/omaha,google/omaha,google/omaha,google/omaha,google/omaha