After https://github.com/llvm/llvm-project/pull/80007 Fuchsia builds are now always building cxx_shared for arm64 and x64 Linux. Ultimately, this is because the LIBCXX_ENABLE_SHARED is not used in compiler-rt to select the correct libc++ target, and because cxx_shared is now always defined, it is selected as a dependency when building runtimes tests. --------- Co-authored-by: Petr Hosek <phosek@google.com>