Merge "first_stage_init: Add SIGCHLD handler in first_stage_console"

void StartConsole(const std::string& cmdline) {

    bool console = KernelConsolePresent(cmdline);

    // Use a simple sigchld handler -- first_stage_console doesn't need to track or log zombies

    const struct sigaction chld_act { .sa_handler = SIG_DFL, .sa_flags = SA_NOCLDWAIT };

    sigaction(SIGCHLD, &chld_act, nullptr);

    pid_t pid = fork();

    if (pid != 0) {

        int status;