How do I fix plugin / cocoapod issue in Cloud Build - GADRewardBasedVideoAd / AdMob

Locally my app builds fine with XCode 10, everything works including the Google Ads, but when I build with Cloud Build I get

961: Compiling JSONModelError.m
962: /BUILD_PATH/appbite.hext.default-ios/temp.XXXXXX20181109-5722-1qwk471/Libraries/Plugins/IOS/GADURewardBasedVideoAd.m:55:25: property 'userIdentifier' not found on object of type 'GADRewardBasedVideoAd *'

I've done a bunch of Googling and reading blogs and posts and they mention I should do
pod repo update
and indeed doing that locally on my Mac gives me
HEAD is now at dc3f6d8d7e1 [Add] ADMobGenSDK 1.3.4

Cool, but SourceTree is telling me nothing changed in my Project's directory, so I've got no update to push up to the repo.

Various forum threads mention Cloud Build does a 'pod install', so how do I make it run this pod repo update?
I've tried Clean builds, changing the version of XCode, but no luck kicking it over.

The leads off to the Xcode Manipulation API & the plist really have me scratching my head.
So if those are the answer could someone give me the "for Dummies" version please. While I do have a background as a Linux guy, my Mac / XCode usage is really boot the machine, build for my iPhone, shut down machine - which is why I think Unity Cloud build is friggen awesome and 100% worth my Pro subscription.

Thanks!