tools/nolibc/time: create time.h with time()

The time() syscall is used by a few simple applications, and is trivial
to implement based on gettimeofday() that we already have. Let's create
the file to ease porting and provide the function. It never returns any
error, though it may segfault in case of invalid pointer, like other
implementations relying on gettimeofday().

Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>