[turbofan]: Convert StringFromCharCode to var-args style TF builtin

src/interface-descriptors.h

Index: src/interface-descriptors.h
diff --git a/src/interface-descriptors.h b/src/interface-descriptors.h
index 8efe7c8a699cb8bad4eddc9c07c587c2a8ba4ab2..b376df1dbb1f1ac7e1d6166a4f71160f7ea62d9e 100644
--- a/src/interface-descriptors.h
+++ b/src/interface-descriptors.h
@@ -62,6 +62,7 @@ class PlatformInterfaceDescriptor;
   V(AllocateInt8x16)                      \
   V(AllocateUint8x16)                     \
   V(AllocateBool8x16)                     \
+  V(Builtin)                              \
   V(ArrayNoArgumentConstructor)           \
   V(ArraySingleArgumentConstructor)       \
   V(ArrayNArgumentsConstructor)           \
@@ -597,6 +598,15 @@ class AllocateHeapNumberDescriptor : public CallInterfaceDescriptor {
 SIMD128_TYPES(SIMD128_ALLOC_DESC)
 #undef SIMD128_ALLOC_DESC
 
+class BuiltinDescriptor : public CallInterfaceDescriptor {
+ public:
+  DEFINE_PARAMETERS(kNewTarget, kArgumentsCount)
+  DECLARE_DESCRIPTOR_WITH_CUSTOM_FUNCTION_TYPE(BuiltinDescriptor,
+                                               CallInterfaceDescriptor)
+  static const Register ArgumentsCountRegister();
+  static const Register NewTargetRegister();
+};
+
 class ArrayNoArgumentConstructorDescriptor : public CallInterfaceDescriptor {
  public:
   DEFINE_PARAMETERS(kFunction, kAllocationSite, kActualArgumentsCount,