childWaitWindows

fn childWaitWindows(child: *process.Child) process.Child.WaitError!process.Child.Term {
    const handle = child.id.?;

    const alertable_syscall: AlertableSyscall = try .start();
    while (true) switch (windows.ntdll.NtWaitForSingleObject(handle, .TRUE, null)) {
        windows.NTSTATUS.WAIT_0 => break alertable_syscall.finish(),
        .USER_APC, .ALERTED, .TIMEOUT => {
            try alertable_syscall.checkCancel();
            continue;
        },
        else => |status| return alertable_syscall.unexpectedNtstatus(status),
    };

    var info: windows.PROCESS.BASIC_INFORMATION = undefined;
    const term: process.Child.Term = switch (windows.ntdll.NtQueryInformationProcess(
        handle,
        .BasicInformation,
        &info,
        @sizeOf(windows.PROCESS.BASIC_INFORMATION),
        null,
    )) {
        .SUCCESS => .{ .exited = @as(u8, @truncate(@backingInt(info.ExitStatus))) },
        else => .{ .unknown = 0 },
    };

    childCleanupWindows(child);
    return term;
}