This gist demonstrates the CPP2V_* environment variables from
SkyLabsAI/BRiCk PR 246 using only public inputs.
It runs on macOS with native cpp2v, creates a Linux amd64 Ubuntu sysroot from
Docker, installs GCC/G++ 15 and libstdc++ headers inside that container, and
then invokes cpp2v on a small C++ file using std::vector.
Example: