testsuite/vect: Make check more accurate.

Similar to before this modifies a check so we do only match a
vectorization attempt if it succeeded.  On riscv we potentially try
several modes if which some may fail.

gcc/testsuite/ChangeLog:

	* gcc.dg/vect/vect-cond-reduc-4.c: Make check more accurate.

gcc/testsuite/gcc.dg/vect/vect-cond-reduc-4.c

@@ -42,7 +42,6 @@ main (void)
 }
 
 /* { dg-final { scan-tree-dump-times "LOOP VECTORIZED" 2 "vect" } } */
-/* { dg-final { scan-tree-dump-times "optimizing condition reduction with FOLD_EXTRACT_LAST" 2 "vect" { target { vect_fold_extract_last && vect_pack_trunc } } } } */
-/* { dg-final { scan-tree-dump-times "optimizing condition reduction with FOLD_EXTRACT_LAST" 4 "vect" { target { { vect_fold_extract_last } && { ! vect_pack_trunc } } } } } */
+/* { dg-final { scan-tree-dump-times "optimizing condition reduction with FOLD_EXTRACT_LAST(?:(?!failed)(?!Re-trying).)*succeeded" 2 "vect" { target { vect_fold_extract_last && vect_pack_trunc } } } } */
 /* { dg-final { scan-tree-dump-times "condition expression based on integer induction." 2 "vect" { target { ! vect_fold_extract_last } } } } */