Function fs_get_cache_directory

tools/rpc/rpc-server.cpp:126–170

NOTE: this is copied from common.cpp to avoid linking with libcommon

// NOTE: this is copied from common.cpp to avoid linking with libcommon
static std::string fs_get_cache_directory() {
    std::string cache_directory = "";
    auto ensure_trailing_slash = [](std::string p) {
        // Make sure to add trailing slash
        if (p.back() != DIRECTORY_SEPARATOR) {
            p += DIRECTORY_SEPARATOR;
        }
        return p;
    };
    if (getenv("LLAMA_CACHE")) {
        cache_directory = std::getenv("LLAMA_CACHE");
    } else {
#if defined(__linux__) || defined(__FreeBSD__) || defined(_AIX) || \
    defined(__OpenBSD__) || defined(__NetBSD__)
        if (std::getenv("XDG_CACHE_HOME")) {
            cache_directory = std::getenv("XDG_CACHE_HOME");
        } else if (std::getenv("HOME")) {
            cache_directory = std::getenv("HOME") + std::string("/.cache/");
        } else {
#if defined(__linux__)
            /* no $HOME is defined, fallback to getpwuid */
            struct passwd *pw = getpwuid(getuid());
            if ((!pw) || (!pw->pw_dir)) {
                throw std::runtime_error("Failed to find $HOME directory");
            }

            cache_directory = std::string(pw->pw_dir) + std::string("/.cache/");
#else /* defined(__linux__) */
            throw std::runtime_error("Failed to find $HOME directory");
#endif /* defined(__linux__) */
        }
#elif defined(__APPLE__)
        cache_directory = std::getenv("HOME") + std::string("/Library/Caches/");
#elif defined(_WIN32)
        cache_directory = std::getenv("LOCALAPPDATA");
#elif defined(__EMSCRIPTEN__)
        GGML_ABORT("not implemented on this platform");
#else
#  error Unknown architecture
#endif
        cache_directory = ensure_trailing_slash(cache_directory);
        cache_directory += "llama.cpp";
    }
    return ensure_trailing_slash(cache_directory);
}

struct rpc_server_params {
    std::string              host        = "127.0.0.1";