[BUG] nc-1.4.0 Build fails on clang

[jgabaut]

When trying to build nc-1.4.0 with clang an error occurs (given we have -Werror):

src/rooms.c:957:63: error: format string is not a string literal (potentially insecure) [-Werror,-Wformat-security]
                            mvwprintw(notifications_win, 0, 0,time_str);
                                                              ^~~~
src/rooms.c:957:63: note: treat the string as an argument to avoid this
                            mvwprintw(notifications_win, 0, 0,time_str);
                                                              ^
                                                              "%s", 
src/rooms.c:1831:59: error: format string is not a string literal (potentially insecure) [-Werror,-Wformat-security]
                        mvwprintw(notifications_win, 0, 0,time_str);
                                                          ^~~~
src/rooms.c:1831:59: note: treat the string as an argument to avoid this
                        mvwprintw(notifications_win, 0, 0,time_str);
                                                          ^
                                                          "%s", 
2 errors generated