[csa] Return last value from BuildFastLoop to allow chaining sequential loops

src/code-stub-assembler.cc

Index: src/code-stub-assembler.cc
diff --git a/src/code-stub-assembler.cc b/src/code-stub-assembler.cc
index 5537d0a9b0f3412325cf5f315344b6cd74269bda..bfd6daf2353cc610f6eaac03bae31e9a907a3361 100644
--- a/src/code-stub-assembler.cc
+++ b/src/code-stub-assembler.cc
@@ -6250,7 +6250,7 @@ Node* CodeStubAssembler::CreateWeakCellInFeedbackVector(Node* feedback_vector,
   return cell;
 }
 
-void CodeStubAssembler::BuildFastLoop(
+Node* CodeStubAssembler::BuildFastLoop(
     const CodeStubAssembler::VariableList& vars,
     MachineRepresentation index_rep, Node* start_index, Node* end_index,
     const FastLoopBody& body, int increment, IndexAdvanceMode mode) {
@@ -6279,6 +6279,7 @@ void CodeStubAssembler::BuildFastLoop(
     Branch(WordNotEqual(var.value(), end_index), &loop, &after_loop);
   }
   Bind(&after_loop);
+  return var.value();
 }
 
 void CodeStubAssembler::BuildFastFixedArrayForEach(