[Interpreter] Add ForInPrepare runtime function which returns a ObjectTriple.

src/compiler/linkage.cc

Index: src/compiler/linkage.cc
diff --git a/src/compiler/linkage.cc b/src/compiler/linkage.cc
index 2eef9291e988e8dfb94da2a6a3b85b87c4488a94..492f1aada02ce628096a4c45e3d31b04cc46e0a2 100644
--- a/src/compiler/linkage.cc
+++ b/src/compiler/linkage.cc
@@ -242,6 +242,9 @@ CallDescriptor* Linkage::GetRuntimeCallDescriptor(
   if (locations.return_count_ > 1) {
     locations.AddReturn(regloc(kReturnRegister1));
   }
+  if (locations.return_count_ > 2) {
+    locations.AddReturn(regloc(kReturnRegister2));
+  }
   for (size_t i = 0; i < return_count; i++) {
     types.AddReturn(MachineType::AnyTagged());
   }
@@ -448,6 +451,9 @@ CallDescriptor* Linkage::GetStubCallDescriptor(
   if (locations.return_count_ > 1) {
     locations.AddReturn(regloc(kReturnRegister1));
   }
+  if (locations.return_count_ > 2) {
+    locations.AddReturn(regloc(kReturnRegister2));
+  }
   for (size_t i = 0; i < return_count; i++) {
     types.AddReturn(return_type);
   }