[rubygems/rubygems] Explicitly load build_metadata.rb because Spec::BuildMetadata is only called from BundlerBuilder.

The current code is broken to call Spec::Builders#build_* method directly.

https://github.com/rubygems/rubygems/commit/4922ae40dd

spec/bundler/spec_helper.rb

@@ -16,7 +16,6 @@ require "rspec/mocks"
 require "rspec/support/differ"
 
 require_relative "support/builders"
-require_relative "support/build_metadata"
 require_relative "support/checksums"
 require_relative "support/filters"
 require_relative "support/helpers"

spec/bundler/support/builders.rb

@@ -3,6 +3,8 @@
 require "bundler/shared_helpers"
 require "shellwords"
 
+require_relative "build_metadata"
+
 module Spec
   module Builders
     def self.extended(mod)