CocoaPods无法找到与“Firebase/CoreOnly”这个库兼容的版本。

我已经将我的Flutter包更新到最新版本，现在IOS不再工作。

当我尝试更新Pods时，它显示以下错误：

    [!] CocoaPods could not find compatible versions for pod "Firebase/CoreOnly":
    In Podfile:
    cloud_firestore (from `.symlinks/plugins/cloud_firestore/ios`) was resolved to 0.0.1, which depends on
    Firebase/Firestore (~> 6.0) was resolved to 6.0.0, which depends on
    Firebase/CoreOnly (= 6.0.0)
    cloud_functions (from `.symlinks/plugins/cloud_functions/ios`) was resolved to 0.0.1, which depends on
    Firebase/Functions (~> 5.18) was resolved to 5.18.0, which depends on
    Firebase/CoreOnly (= 5.18.0)

这是我的pubspec.yaml（与Firebase有关）：

firebase_core: "^0.4.0"
firebase_auth: "^0.11.0"
firebase_analytics: "^3.0.0"  
cloud_firestore: "^0.11.0+1"
cloud_functions: "^0.3.0"
firebase_storage: "^3.0.0"
firebase_messaging: "^5.0.1"

我已经采取了各种步骤来尝试修复：

flutter clean
flutter build ios
pod install
pod update
pod repo update
pod install --repo-update

我在Podfile和Xcode中将平台设置为：ios,\'12.1\'，但仍然无法运行。

这是我的podfile：

# Uncomment this line to define a global platform for your project
platform :ios, '12.1'
# CocoaPods analytics sends network stats synchronously affecting flutter build latency.
ENV['COCOAPODS_DISABLE_STATS'] = 'true'
project 'Runner', {
  'Debug' => :debug,
  'Profile' => :release,
  'Release' => :release,
}
def parse_KV_file(file, separator='=')
  file_abs_path = File.expand_path(file)
  if !File.exists? file_abs_path
    return [];
  end
  pods_ary = []
  skip_line_start_symbols = ["#", "/"]
  File.foreach(file_abs_path) { |line|
      next if skip_line_start_symbols.any? { |symbol| line =~ /^\s*#{symbol}/ }
      plugin = line.split(pattern=separator)
      if plugin.length == 2
        podname = plugin[0].strip()
        path = plugin[1].strip()
        podpath = File.expand_path("#{path}", file_abs_path)
        pods_ary.push({:name => podname, :path => podpath});
      else
        puts "Invalid plugin specification: #{line}"
      end
  }
  return pods_ary
end
target 'Runner' do
  use_frameworks!
  # Prepare symlinks folder. We use symlinks to avoid having Podfile.lock
  # referring to absolute paths on developers' machines.
  system('rm -rf .symlinks')
  system('mkdir -p .symlinks/plugins')
  # Flutter Pods
  generated_xcode_build_settings = parse_KV_file('./Flutter/Generated.xcconfig')
  if generated_xcode_build_settings.empty?
    puts "Generated.xcconfig must exist. If you're running pod install manually, make sure flutter packages get is executed first."
  end
  generated_xcode_build_settings.map { |p|
    if p[:name] == 'FLUTTER_FRAMEWORK_DIR'
      symlink = File.join('.symlinks', 'flutter')
      File.symlink(File.dirname(p[:path]), symlink)
      pod 'Flutter', :path => File.join(symlink, File.basename(p[:path]))
    end
  }
  # Plugin Pods
  plugin_pods = parse_KV_file('../.flutter-plugins')
  plugin_pods.map { |p|
    symlink = File.join('.symlinks', 'plugins', p[:name])
    File.symlink(p[:path], symlink)
    pod p[:name], :path => File.join(symlink, 'ios')
  }
end
post_install do |installer|
  installer.pods_project.targets.each do |target|
    target.build_configurations.each do |config|
      config.build_settings['ENABLE_BITCODE'] = 'NO'
    end
  end
end