Gem::Package#build

# File tmp/rubies/ruby-3.4.1/lib/rubygems/package.rb, line 292
  def build(skip_validation = false, strict_validation = false)
    raise ArgumentError, "skip_validation = true and strict_validation = true are incompatible" if skip_validation && strict_validation

    Gem.load_yaml

    @spec.validate true, strict_validation unless skip_validation

    setup_signer(
      signer_options: {
        expiration_length_days: Gem.configuration.cert_expiration_length_days,
      }
    )

    @gem.with_write_io do |gem_io|
      Gem::Package::TarWriter.new gem_io do |gem|
        add_metadata gem
        add_contents gem
        add_checksums gem
      end
    end

    say <<-EOM
  Successfully built RubyGem
  Name: #{@spec.name}
  Version: #{@spec.version}
  File: #{File.basename @gem.path}
EOM
  ensure
    @signer = nil
  end