overload_test needs some extra dependencies to build when absl::variant
is not an alias for std::variant; these dependencies are listed in
absl/functional/BUILD.bazel but not in absl/functional/CMakeLists.txt.
Copy dependencies from BUILD.bazel to CMakeLists.txt.

PiperOrigin-RevId: 631845552
Change-Id: I63f53323b28aff36530be645b312e94b24475f53