[ORC] Fix EPCGenericMemoryAccessTest write-ptrs implementation after f93df5ebd9

The write-pointers operation should be writing a pointer, not a uint64_t. This
bug existed prior to f93df5ebd9, but changes in that commit seem to have
exposed the issue (see e.g.
https://lab.llvm.org/buildbot/#/builders/154/builds/17956).

llvm/unittests/ExecutionEngine/Orc/EPCGenericMemoryAccessTest.cpp

@@ -34,7 +34,7 @@ CWrapperFunctionResult testWritePointers(const char *ArgData, size_t ArgSize) {
       handle(ArgData, ArgSize,
              [](std::vector<tpctypes::PointerWrite> Ws) {
                for (auto &W : Ws)
-                 *W.Addr.template toPtr<uint64_t *>() = W.Value.getValue();
+                 *W.Addr.template toPtr<void **>() = W.Value.toPtr<void *>();
              })
           .release();
 }