another attempt to make the test more robust

testsuite/tests/ghc-regress/concurrent/should_run/conc024.hs

@@ -3,6 +3,7 @@ module Main where
 import Control.Exception
 import Control.Concurrent
 import Prelude hiding (catch)
+import System.Mem
 
 -- illustrates the BlockOnDeadMVar exception
 
@@ -10,5 +11,5 @@ main = do
   id <- myThreadId
   forkIO (catch (do m <- newEmptyMVar; takeMVar m)
 		(\e -> throwTo id (e::SomeException)))
-  catch (threadDelay 1000000)
+  catch (do yield; performGC; threadDelay 1000000)
 	(\e -> print (e::SomeException))