testsuite: Make T3234 more robust

Just look for the rule firing that we want to see instead of matching on
the entire dump.

Fixes #15088.

testsuite/tests/simplCore/should_compile/Makefile

@@ -13,6 +13,10 @@ T13468:
         # Expecting no output from the grep, hence "-"
         # If the case branch is not eliminated, we get a patError
 
+T3234:
+	$(RM) -f T3234.o T3234.hi
+	'$(TEST_HC)' $(TEST_HC_OPTS) -O -c -ddump-simpl-stats T3234.hs | grep 'fold/build'
+
 T3990:
 	$(RM) -f T3990.o T3990.hi
 	'$(TEST_HC)' $(TEST_HC_OPTS) -O -c -ddump-simpl T3990.hs | grep 'test_case'

testsuite/tests/simplCore/should_compile/T3234.stderr

-
-==================== FloatOut stats: ====================
-2 Lets floated to top level; 0 Lets floated elsewhere; from 1 Lambda groups
-
-
-
-==================== FloatOut stats: ====================
-0 Lets floated to top level; 0 Lets floated elsewhere; from 0 Lambda groups
-
-
-
-==================== Grand total simplifier statistics ====================
-Total ticks:     52
-
-18 PreInlineUnconditionally
-  1 g
-  1 xs
-  1 ys
-  1 c
-  1 n
-  1 a
-  1 a
-  1 g
-  1 h
-  1 n
-  1 k
-  1 z
-  1 g
-  1 c
-  1 n
-  1 lvl
-  1 lvl
-  1 lvl
-1 PostInlineUnconditionally 1 c
-1 UnfoldingDone 1 GHC.Base.build
-5 RuleFired
-  1 ++
-  1 augment/build
-  1 fold/build
-  1 unpack
-  1 unpack-list
-2 LetFloatFromLet 2
-25 BetaReduction
-  1 a
-  1 g
-  1 a
-  1 xs
-  1 ys
-  1 b
-  1 c
-  1 n
-  1 a
-  1 b
-  1 a
-  1 a
-  1 g
-  1 h
-  1 b
-  1 c
-  1 n
-  1 b
-  1 a
-  1 k
-  1 z
-  1 g
-  1 a
-  1 c
-  1 n
-10 SimplifierDone 10
-
-

testsuite/tests/simplCore/should_compile/T3234.stdout

+  1 fold/build
\ No newline at end of file

testsuite/tests/simplCore/should_compile/all.T

@@ -44,9 +44,9 @@ test('T3016', when(fast(), skip), compile, [''])
 test('T1647', normal, compile, ['-fdicts-strict -dcore-lint'])
 
 test('T3234',
-     only_ways(['optasm']),
-     compile,
-     ['-ddump-simpl-stats -dsuppress-uniques'])
+     normal,
+     run_command,
+     ['$MAKE -s --no-print-directory T3234'])
 
 test('T3717', only_ways(['optasm']),
               compile,