Azure pipeline error: No `Podfile' found in the project directory

I am trying to create CI/CD pipeline, for Flutter iOS app using azure-pipelines.yml file.
Everything is OK in android studio and Xcode.
But when I try to build ios app in Azure DevOps I get this error:

/usr/local/lib/ruby/gems/2.7.0/bin/pod --version
1.11.3
/usr/local/lib/ruby/gems/2.7.0/bin/pod install --repo-update
[!] No `Podfile' found in the project directory.
##[error]The process '/usr/local/lib/ruby/gems/2.7.0/bin/pod' failed with exit code 1
##[error]The 'pod' command failed with error: The process '/usr/local/lib/ruby/gems/2.7.0/bin/pod' failed with exit code 1
Finishing: CocoaPods

My azure-pipelines.yml file is:

- task: InstallAppleCertificate@2
  inputs:
    certSecureFile: '$(p12FileName)'
    certPwd: '$(p12Password)'
    keychain: 'temp'
    deleteCert: true  

- task: InstallAppleProvisioningProfile@1
  displayName: "Install provisioning file"
  inputs:
    provisioningProfileLocation: 'secureFiles'
    provProfileSecureFile: '$(provisioningProfile)'

- task: CocoaPods@0
  inputs:
    forceRepoUpdate: true

- task: Xcode@5
  displayName: 'Xcode task'
  inputs:
    actions: 'build'
    sdk: 
    configuration: 'Release'
    xcWorkspacePath: '**/*.xcodeproj/project.xcworkspace'
    xcodeVersion: '12'
    packageApp: true
    signingOption: 'manual'
    signingIdentity: '$(APPLE_CERTIFICATE_SIGNING_IDENTITY)'
    provisioningProfileUuid: '$(APPLE_PROV_PROFILE_UUID)'

- task: FlutterInstall@0
  displayName: "Install Flutter SDK"
  inputs:
    mode: 'auto'
    channel: 'stable'
    version: 'latest'

- task: FlutterBuild@0
  displayName: "Build application"
  inputs:
    target: ipa
    projectDirectory: '$(Build.SourcesDirectory)'
    exportOptionsPlist: 'ios/exportOptions.plist'

and this is myPodfile:

platform :ios, '12.0'

ENV['COCOAPODS_DISABLE_STATS'] = 'true'

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

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

def flutter_install_ios_plugin_pods(ios_application_path = nil)
  ios_application_path ||= File.dirname(defined_in_file.realpath) if self.respond_to?(:defined_in_file)
  raise 'Could not find iOS application path' unless ios_application_path

  symlink_dir = File.expand_path('.symlinks', ios_application_path)
  system('rm', '-rf', symlink_dir) # Avoid the complication of dependencies like FileUtils.

  symlink_plugins_dir = File.expand_path('plugins', symlink_dir)
  system('mkdir', '-p', symlink_plugins_dir)

  plugins_file = File.join(ios_application_path, '..', '.flutter-plugins-dependencies')
  plugin_pods = flutter_parse_plugins_file(plugins_file)
  plugin_pods.each do |plugin_hash|
    plugin_name = plugin_hash['name']
    plugin_path = plugin_hash['path']
    if (plugin_name && plugin_path)
      symlink = File.join(symlink_plugins_dir, plugin_name)
      File.symlink(plugin_path, symlink)

      if plugin_name == 'flutter_ffmpeg'
          pod 'flutter_ffmpeg/full-lts', :path => File.join('.symlinks', 'plugins', plugin_name, 'ios')
      else
          pod plugin_name, :path => File.join('.symlinks', 'plugins', plugin_name, 'ios')
      end
    end
  end
end

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.build_configurations.each do |config|
    config.build_settings['PROVISIONING_PROFILE_SPECIFIER'] = ''
    config.build_settings['CODE_SIGNING_ALLOWED'] = 'NO'
    config.build_settings['CODE_SIGNING_REQUIRED'] = 'NO'
  end
  installer.pods_project.targets.each do |target|
    target.build_configurations.each do |config|
        config.build_settings['PROVISIONING_PROFILE_SPECIFIER'] = ''
        config.build_settings['CODE_SIGNING_ALLOWED'] = 'NO'
        config.build_settings['CODE_SIGNING_REQUIRED'] = 'NO'
    end
  end
end

If I add

workingDirectory: '$(Build.SourcesDirectory)/ios'

I will get this error message:

"Invalid Podfile file: /Users/runner/work/1/s/ios/Flutter/Generated.xcconfig must exist. If you're running pod install manually, make sure flutter pub get is executed first."