[tlively]

GitHub Actions recently updated ubuntu-latest to Ubuntu 26.04, which ships GCC 15's libstdc++ headers without transitive <cstdint> includes. The previously pinned FuzzTest submodule fetched abseil-cpp 20240116.0, which failed to compile under GCC 15's libstdc++ due to a missing uintptr_t declaration in absl/container/internal/container_memory.h.

Update third_party/fuzztest to the 2026-06-29 release tag (which updates abseil-cpp to 20260526.0) along with two compatibility fixes:

1. Inherit std::variant constructors via using variant::variant; in the std::variant wrapper structs in test/gtest/type-domains.h, as FuzzTest's VariantOfImpl::GetValue now constructs custom variant types using std::in_place_index<I>.

2. Restore Binaryen's CMAKE_CXX_STANDARD (20) when configuring Abseil via CMAKE_PROJECT_absl_INCLUDE in third_party/CMakeLists.txt. FuzzTest's CMakeLists.txt unconditionally sets CMAKE_CXX_STANDARD to 17, which otherwise builds libabsl_status with C++17 absl::SourceLocation while binaryen-unittests compiles with C++20 std::source_location, causing an ABI link mismatch. With ABSL_PROPAGATE_CXX_STD enabled, configuring Abseil with C++20 also propagates -std=c++20 to FuzzTest.

[tlively]

If this doesn't seem worth the complexity, we can just delete fuzztest instead. It's still used only experimentally and is not load bearing. But I think it might be worth keeping around in case we want to use it more in the future.