Include debug logging of string conversions

lib/vagrant/util/safe_exec.rb

@@ -42,8 +42,11 @@ module Vagrant
           else
             if Vagrant::Util::Platform.windows?
               # Re-generate strings to ensure common encoding
+              @@logger.debug("Converting command and arguments to common UTF-8 encoding for exec.")
+              @@logger.debug("Command: `#{command.inspect}` Args: `#{args.inspect}`")
               command = "#{command}".force_encoding("UTF-8")
               args = args.map{|arg| "#{arg}".force_encoding("UTF-8") }
+              @@logger.debug("Converted - Command: `#{command.inspect}` Args: `#{args.inspect}`")
             end
             Kernel.exec(command, *args)
           end