[turbofan] Make new.target explicit in JSCallDescriptor.

src/x64/macro-assembler-x64.h

Index: src/x64/macro-assembler-x64.h
diff --git a/src/x64/macro-assembler-x64.h b/src/x64/macro-assembler-x64.h
index 5d66c6ec1e228891db7f9cef0e293977d34091ad..7c3ae7ce0b799f05f4eda23bc83289d1e71eec2c 100644
--- a/src/x64/macro-assembler-x64.h
+++ b/src/x64/macro-assembler-x64.h
@@ -26,6 +26,7 @@ const Register kInterpreterBytecodeOffsetRegister = {Register::kCode_r12};
 const Register kInterpreterBytecodeArrayRegister = {Register::kCode_r14};
 const Register kInterpreterDispatchTableRegister = {Register::kCode_r15};
 const Register kJavaScriptCallArgCountRegister = {Register::kCode_rax};
+const Register kJavaScriptCallNewTargetRegister = {Register::kCode_rdx};
 const Register kRuntimeCallFunctionRegister = {Register::kCode_rbx};
 const Register kRuntimeCallArgCountRegister = {Register::kCode_rax};