warning: The iOS Simulator deployment target 'IPHONEOS_DEPLOYMENT_TARGET' is set to 4.3, but the range of supported deployment target versions is 9.0 to 14.3.99. (in target 'FMDB' from project 'Pods')

将下述内容添加在PodFile的最下方，重新执行Pod install。

post_install do |installer|
  installer.pods_project.targets.each do |target|
    target.build_configurations.each do |config|
      if config.build_settings['IPHONEOS_DEPLOYMENT_TARGET'].to_f < 9.0
        config.build_settings['IPHONEOS_DEPLOYMENT_TARGET'] = '9.0'
      end
    end
  end
end

注意：修改版本号与你的 platform :ios, '9.0' 一致。