Tried to upgrade the iOS version on Flutter. Build failed

I tried to change my Flutter version from the podfile and also tried to change it in Xcode's Build Settings. I changed it from 9.0 to 12.0. Then when I run the app, I am getting all sorts of errors.

Here is my Podfile:

# Uncomment this line to define a global platform for your project
platform :ios, '12.0'

# CocoaPods analytics sends network stats synchronously affecting flutter build latency.
ENV['COCOAPODS_DISABLE_STATS'] = 'true'

project 'Runner', {
  'Debug' => :debug,
  'Profile' => :release,
  'Release' => :release,
}

pod 'Firebase/Analytics'
pod 'Firebase/Auth'
pod 'Firebase/Firestore'
pod 'Firebase/Storage'
pod 'Firebase/Database' 

def flutter_root
  generated_xcode_build_settings_path = File.expand_path(File.join('..', 'Flutter', 'Generated.xcconfig'), __FILE__)
  unless File.exist?(generated_xcode_build_settings_path)
    raise "#{generated_xcode_build_settings_path} must exist. If you're running pod install manually, make sure flutter pub get is executed first"
  end

  File.foreach(generated_xcode_build_settings_path) do |line|
    matches = line.match(/FLUTTER_ROOT\=(.*)/)
    return matches[1].strip if matches
  end
  raise "FLUTTER_ROOT not found in #{generated_xcode_build_settings_path}. Try deleting Generated.xcconfig, then run flutter pub get"
end

require File.expand_path(File.join('packages', 'flutter_tools', 'bin', 'podhelper'), flutter_root)

flutter_ios_podfile_setup

target 'Runner' do
  use_frameworks!
  use_modular_headers!

  flutter_install_all_ios_pods File.dirname(File.realpath(__FILE__))
end

post_install do |installer|
  installer.pods_project.targets.each do |target|
    flutter_additional_ios_build_settings(target)
    target.build_configurations.each do |config|
       config.build_settings['IPHONEOS_DEPLOYMENT_TARGET'] = '12.0'
    end
  end
end

Then this is what I am getting in my Flutter log when I try to build the iOS app I am not sure if I properly did it or made some error. But I would greatly appreciate anyone who does offer to help in this regards. I am just trying to upgrade the minimum iOS version.