Placing these tests in anonymous namespaces, is the suggested fix
according to the GCC documentation.

The GCC documentation states: "If a type A depends on a type B with no or
 internal linkage, defining it in multiple translation units would be an
ODR violation because the meaning of B is different in each translation unit.
If A only appears in a single translation unit, the best way to silence the
warning is to give it internal linkage by putting it in an anonymous namespace as well."

Change-Id: I69a1e9b5f1789e9a7a62c762cd499809a72e0ea5
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1836255
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64128}