Podfile in real-world example

source 'https://cdn.cocoapods.org/'

platform :ios, :deployment_target => '11.0'  
inhibit_all_warnings!

project 'your_project_name', 'Variant Debug' => :debug, 'Variant Release' => :release

target 'your_target' do  
    project 'your_project_name'
    pod 'HysteriaPlayer',                       '~> 2.2.2'
    pod 'SDWebImage',                           '~> 4.0.0'
    ...

    pod 'some_private_pod', :git => 'https://github.com/some/pod.git', :commit => '142789f795def15ba7282bf73e83cf777a29a8e0'

    target :your_test_target do
        inherit! :search_paths
        pod 'Aspects',                          '~> 1.4.1'
    end
end

post_install do |installer|  
    installer.pods_project.root_object.attributes['LastSwiftMigration'] = 9999
    installer.pods_project.root_object.attributes['LastSwiftUpdateCheck'] = 9999
    installer.pods_project.root_object.attributes['LastUpgradeCheck'] = 9999
    installer.pods_project.targets.each do |target|
        target.build_configurations.each do |config|
            config.build_settings.delete 'IPHONEOS_DEPLOYMENT_TARGET'
            config.build_settings.delete('ARCHS')
        end
    end
end  

Detailed explanation

source 'https://cdn.cocoapods.org/'

If you're still targeting your pod specs trunk to https://github.com/CocoaPods/Specs.git, you better switch to https://cdn.cocoapods.org/ for speed up pod install process.

ref: offical changelog

project 'your_project_name', 'Variant Debug' => :debug, 'Variant Release' => :release'

If you have build configurations other than default Debug and Release, you need to specify which build type of it should be used so that CocoaPods could set build setting attributes correctly. For example, Enable Testability and Build Active Architecture Only attribute only set YES on Debug build type.

post_install

    installer.pods_project.root_object.attributes['LastSwiftMigration'] = 9999
    installer.pods_project.root_object.attributes['LastSwiftUpdateCheck'] = 9999
    installer.pods_project.root_object.attributes['LastUpgradeCheck'] = 9999

If your pod contained static library compiled by older Swift version than your project. Xcode will likely give you a Swift conversion warning, but there's nothing you can do about it.
This strange setting aims to suppress the Swift conversion warning.

Ref: https://github.com/CocoaPods/CocoaPods/issues/8674#issuecomment-524097348

installer.pods_project.targets.each do |target|  
        target.build_configurations.each do |config|
            config.build_settings.delete 'IPHONEOS_DEPLOYMENT_TARGET'
            config.build_settings.delete 'ARCHS'
        end
    end

Preventing pod target overrides Pods project build setting. This could be fixed on the newer CocoaPods version, check before you add those configs.