Merge pull request #38939 from hammerdr/38937

Load XML Builder if it is not available

activesupport/lib/active_support/core_ext/hash/conversions.rb

@@ -73,7 +73,7 @@ class Hash
   # configure your own builder with the <tt>:builder</tt> option. The method also accepts
   # options like <tt>:dasherize</tt> and friends, they are forwarded to the builder.
   def to_xml(options = {})
-    require "active_support/builder" unless defined?(Builder)
+    require "active_support/builder" unless defined?(Builder) && defined?(Builder::XmlMarkup)
 
     options = options.dup
     options[:indent]  ||= 2