[turbofan] Ensure stackcheck flags do something.

src/compiler/pipeline.cc

Index: src/compiler/pipeline.cc
diff --git a/src/compiler/pipeline.cc b/src/compiler/pipeline.cc
index 3a542e6890b5825036b5d54ccda37d404a8ecf9a..12a0780021c15ec855017389c9743957ad62078a 100644
--- a/src/compiler/pipeline.cc
+++ b/src/compiler/pipeline.cc
@@ -1360,13 +1360,17 @@ void Pipeline::AllocateRegisters(const RegisterConfiguration* config,
     CHECK(!data->register_allocation_data()->ExistsUseWithoutDefinition());
   }
 
-  Run<SplinterLiveRangesPhase>();
+  if (FLAG_turbo_preprocess_ranges) {
+    Run<SplinterLiveRangesPhase>();
+  }
 
   // TODO(mtrofin): re-enable greedy once we have bots for range preprocessing.
   Run<AllocateGeneralRegistersPhase<LinearScanAllocator>>();
   Run<AllocateDoubleRegistersPhase<LinearScanAllocator>>();
 
-  Run<MergeSplintersPhase>();
+  if (FLAG_turbo_preprocess_ranges) {
+    Run<MergeSplintersPhase>();
+  }
 
   if (FLAG_turbo_frame_elision) {
     Run<LocateSpillSlotsPhase>();