gnat.adc: Do not generate assertion code for Refined_Post

Ada usually does lots of type and contract checking during runtime. As
this produces overhead and there is nobody to tell when we run into an
exception, we disable code generation for those checks. Now disable it
for `Refined_Post` too, which was just missed earlier.

Change-Id: I67ca754f830e387efee3930e86929eb494bfaf03
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/16945
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>

gnat.adc

@@ -35,6 +35,7 @@ pragma Restrictions (Static_Storage_Size);
 pragma Assertion_Policy
   (Statement_Assertions => Disable,
    Pre                  => Disable,
-   Post                 => Disable);
+   Post                 => Disable,
+   Refined_Post         => Disable);
 pragma Overflow_Mode (General => Strict, Assertions => Eliminated);
 pragma SPARK_Mode (On);