Avoid printing char16_t* and wchar_t to gtest Message

gtest's Message class has a special handler for operator<< of wchar_t*
to convert it to UTF-8, but it doesn't have one for a single wchar_t or
for a char16_t* string. It delegates these to std::stringstream, which
as of a libc++ upgrade, deletes its operator<< for char16_t and
wchar_t. See wg21.link/p1423r3.

Bug: http://b/175635923
Test: m MODULES-IN-bionic
Change-Id: I8307663b72855cfc0b91d7f63993f1f6fe028b8e
diff --git a/tests/malloc_test.cpp b/tests/malloc_test.cpp
index 14a426f..2b48d85 100644
--- a/tests/malloc_test.cpp
+++ b/tests/malloc_test.cpp
@@ -935,7 +935,8 @@
   size_t expected_alignment = alignof(Type);
   if (expected_alignment != 0) {
     ASSERT_EQ(0U, (expected_alignment - 1) & reinterpret_cast<uintptr_t>(floating))
-        << "Expected alignment " << expected_alignment << " ptr value " << floating;
+        << "Expected alignment " << expected_alignment << " ptr value "
+        << static_cast<void*>(floating);
   }
 }