[flutter] Ignoring ffi-1.15.4 because its extensions are not built. Try: gem pristine ffi --version 1.15.4

자세히 봤더니 그 위 부터 에러가 있었음

[!] CocoaPods could not find compatible versions for pod "firebase_messaging":
      In Podfile:
        firebase_messaging (from `.symlinks/plugins/firebase_messaging/ios`)

해결 :: https://github.com/FirebaseExtended/flutterfire/issues/4709

As mentioned in the changelog the minimum deployment target is now iOS 10.
Go to your Podfile and uncomment
# platform :ios, '9.0'
Then change the version to 10
platform :ios, '10.0'

>> 2가지를 고침 xcode 에서 deployment target을 iOS 10으로 고치고 아래와 같이 실행
>> 그리고 나서 
1. flutter clean
2. pod update