Rebuild command and arguments before exec on Windows

Flat command can cause issues with arguments. Creating new
string instances from arguments forces common encoding of
all strings used for exec.

Fixes #8690

lib/vagrant/util/safe_exec.rb

@@ -41,14 +41,11 @@ module Vagrant
             end
           else
             if Vagrant::Util::Platform.windows?
-              @@logger.debug("Converting command and arguments to single string for exec")
-              @@logger.debug("Command: `#{command.inspect}` Args: `#{args.inspect}`")
-              full_command = "#{command} #{args.join(" ")}"
-              @@logger.debug("Converted command: #{full_command}")
-              Kernel.exec(full_command)
-            else
-              Kernel.exec(command, *args)
+              # Re-generate strings to ensure common encoding
+              command = "#{command}".force_encoding("UTF-8")
+              args = args.map{|arg| "#{arg}".force_encoding("UTF-8") }
             end
+            Kernel.exec(command, *args)
           end
         rescue *rescue_from
           # We retried already, raise the issue and be done