clang: Fix assert on void pointer arithmetic with address_space

This attempted to always use the default address space void pointer
type instead of preserving the source address space.
diff --git a/clang/lib/CodeGen/CGExprScalar.cpp b/clang/lib/CodeGen/CGExprScalar.cpp
index 55a413a2..c1391d4 100644
--- a/clang/lib/CodeGen/CGExprScalar.cpp
+++ b/clang/lib/CodeGen/CGExprScalar.cpp
@@ -3258,7 +3258,7 @@
   // GNU void* casts amount to no-ops since our void* type is i8*, but this is
   // future proof.
   if (elementType->isVoidType() || elementType->isFunctionType()) {
-    Value *result = CGF.Builder.CreateBitCast(pointer, CGF.VoidPtrTy);
+    Value *result = CGF.EmitCastToVoidPtr(pointer);
     result = CGF.Builder.CreateGEP(result, index, "add.ptr");
     return CGF.Builder.CreateBitCast(result, pointer->getType());
   }