How to add .a libraries on flutter plugin via podspec

I am trying to include .a files on the iOS side of the plugin. Below is my file structure.

Now when I try to add .a files via vendored_libraries on podspec, pod install is successfully completed. And when I compile the code, I get Library Not Found -lAccuraFace

I tried to add the .a file on the Link Binary With Libraries section on the build phase on the Pod target. It's still the same, how can I define the podspec in such a way that the .a file is included and linked automatically.

Here is my podspec file for the plugin

Pod::Spec.new do |s|
  s.name             = 'accuraemirates'
  s.version          = '0.0.1'
  s.summary          = 'A new Flutter plugin.'
  s.description      = <<-DESC
A new Flutter plugin.
                       DESC
  s.homepage         = 'http://example.com'
  s.license          = { :file => '../LICENSE' }
  s.author           = { 'Your Company' => 'email@example.com' }
  s.source           = { :path => '.' }
  s.source_files = 'Classes/**/*'
  s.dependency 'Flutter'
  s.public_header_files = 'Classes/*{.h}'
  s.private_header_files = 'Classes/CodeScan/**/*{.h,.cpp,.a}'
  s.platform = :ios, '8.0'
  s.preserve_paths = 'opencv2.framework'
  s.xcconfig = { 
    'OTHER_LDFLAGS' => '-framework opencv2 -lAccuraFace',
  }
  s.ios.vendored_frameworks = 'opencv2.framework', "CoreVideo.framework", "Foundation.framework", "CoreGrpahics.framework", 
  "Accelerate.framework", "CoreMedia.framework", "CoreImage.framework", "QuartzCore.framework", "AudioToolbox.framework", "CoreData.framework", "SystemConfiguration.framework"
  s.ios.vendored_libraries = 'Classes/Framework/*{.a}', "libz.1.dylib", "c++", "stdc++"

  # Flutter.framework does not contain a i386 slice. Only x86_64 simulators are supported.
  s.pod_target_xcconfig = { 'DEFINES_MODULE' => 'YES', 'VALID_ARCHS[sdk=iphonesimulator*]' => 'x86_64' }
  s.swift_version = '5.0'
end

Here is the root podfile

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
  generated_key_values = {}
  skip_line_start_symbols = ["#", "/"]
  File.foreach(file_abs_path) do |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)
      generated_key_values[podname] = podpath
    else
      puts "Invalid plugin specification: #{line}"
    end
  end
  generated_key_values
end

target 'Runner' do
  use_frameworks!
  use_modular_headers!

  # Flutter Pod

  copied_flutter_dir = File.join(__dir__, 'Flutter')
  copied_framework_path = File.join(copied_flutter_dir, 'Flutter.framework')
  copied_podspec_path = File.join(copied_flutter_dir, 'Flutter.podspec')
  unless File.exist?(copied_framework_path) && File.exist?(copied_podspec_path)
    # Copy Flutter.framework and Flutter.podspec to Flutter/ to have something to link against if the xcode backend script has not run yet.
    # That script will copy the correct debug/profile/release version of the framework based on the currently selected Xcode configuration.
    # CocoaPods will not embed the framework on pod install (before any build phases can generate) if the dylib does not exist.

    generated_xcode_build_settings_path = File.join(copied_flutter_dir, 'Generated.xcconfig')
    unless File.exist?(generated_xcode_build_settings_path)
      raise "Generated.xcconfig must exist. If you're running pod install manually, make sure flutter pub get is executed first"
    end
    generated_xcode_build_settings = parse_KV_file(generated_xcode_build_settings_path)
    cached_framework_dir = generated_xcode_build_settings['FLUTTER_FRAMEWORK_DIR'];

    unless File.exist?(copied_framework_path)
      FileUtils.cp_r(File.join(cached_framework_dir, 'Flutter.framework'), copied_flutter_dir)
    end
    unless File.exist?(copied_podspec_path)
      FileUtils.cp(File.join(cached_framework_dir, 'Flutter.podspec'), copied_flutter_dir)
    end
  end

  # Keep pod path relative so it can be checked into Podfile.lock.
  pod 'Flutter', :path => 'Flutter'

  # Plugin Pods

  # 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')
  plugin_pods = parse_KV_file('../.flutter-plugins')
  plugin_pods.each do |name, path|
    symlink = File.join('.symlinks', 'plugins', name)
    File.symlink(path, symlink)
    pod name, :path => File.join(symlink, 'ios')
  end
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

Is it not possible to add/link .a libraries from podspec file on a flutter plugin.

Finally found the issue..

Pod::Spec.new do |s|
  # other obvious values
  s.source_files = 'Classes//*{.h,.a,.swift,.mm,.m,.hpp}'
  s.resources = 'Resources//'
  s.static_framework = true 
  s.public_header_files = "Classes/VideoCamera/VideoCameraWrapperDelegate.h", "Classes/VideoCamera/VideoCameraWrapper.h",'Classes/.h',
  s.private_header_files = 'Classes/CodeScan//{.h,.cpp,.hpp}'
  s.platform = :ios, '8.0'
  s.preserve_paths = 'opencv2.framework', 'Classes/Framework/.a'
  
  s.xcconfig = { 
     # here on LDFLAG, I had to set -l and then the library name (without lib prefix although the file name has it).
    'OTHER_LDFLAGS' => '-framework opencv2 -lc++ -lAccuraFace -lAccuraEmirate -lDocRecog -lz',
    'USER_HEADER_SEARCH_PATHS' => '"${PROJECT_DIR}/.."/',
    "LIBRARY_SEARCH_PATHS" => '"${PROJECT_DIR}/.."/*',
  }
  s.vendored_frameworks = 'opencv2.framework' # Various framworks you need
  # Here the name of the library can include lib as the file name has it too.
  s.vendored_libraries = 'AccuraFace','libAccuraEmirate','libDocRecog'
end

Notice two values here OTHER_LDFLAGS and vendored_libraries. Although I have same file, they need names with and without lib prefix. Weird but worked.