Flush stdout in test case for #10596

which might help, as it has helped with lots of other TH-related test
cases in the past.

testsuite/tests/th/T10596.hs

@@ -2,10 +2,13 @@
 module T10596 where
 import Language.Haskell.TH
 import Language.Haskell.TH.Syntax
+import System.IO
+
 do
   putQ (100 :: Int)
   x <- (getQ :: Q (Maybe Int))
 
   -- It should print "Just 100"
   runIO $ print x
+  runIO $ hFlush stdout
   return []