Generate config for //frc971/wpilib:loop_output_handler_test

This is in preparation for timing reports.

Change-Id: I34b3cd5b2df1bb8b69693ac657ffaede1e794bff
diff --git a/frc971/wpilib/loop_output_handler_test.fbs b/frc971/wpilib/loop_output_handler_test.fbs
index 6cb2cf1..ddd36d0 100644
--- a/frc971/wpilib/loop_output_handler_test.fbs
+++ b/frc971/wpilib/loop_output_handler_test.fbs
@@ -4,3 +4,5 @@
 table LoopOutputHandlerTestOutput {
   voltage:double;
 }
+
+root_type LoopOutputHandlerTestOutput;