Fix uninitialized new.target register in InvokeBuiltin.

src/ppc/macro-assembler-ppc.cc

Index: src/ppc/macro-assembler-ppc.cc
diff --git a/src/ppc/macro-assembler-ppc.cc b/src/ppc/macro-assembler-ppc.cc
index 34a37241fd4aba54d8d772835db79872d04edc49..b5288801edbaccefac4d7679939429afc2b40906 100644
--- a/src/ppc/macro-assembler-ppc.cc
+++ b/src/ppc/macro-assembler-ppc.cc
@@ -2342,6 +2342,9 @@ void MacroAssembler::InvokeBuiltin(int native_context_index, InvokeFlag flag,
   // You can't call a builtin without a valid frame.
   DCHECK(flag == JUMP_FUNCTION || has_frame());
 
+  // Always initialize new target.
+  LoadRoot(r6, Heap::kUndefinedValueRootIndex);
+
   LoadNativeContextSlot(native_context_index, r4);
   LoadP(ip, FieldMemOperand(r4, JSFunction::kCodeEntryOffset));
   if (flag == CALL_FUNCTION) {