lib/test_ubsan.c: VLA no longer used in kernel

Since we now build with -Wvla, any use of VLA throws a warning.
Including this test, so...  maybe we should just remove the test?

  lib/test_ubsan.c: In function 'test_ubsan_vla_bound_not_positive':
  lib/test_ubsan.c:48:2: warning: ISO C90 forbids variable length array 'buf' [-Wvla]

For the out-of-bounds test, switch to non-VLA setup.

  lib/test_ubsan.c: In function 'test_ubsan_out_of_bounds':
  lib/test_ubsan.c:64:2: warning: ISO C90 forbids variable length array 'arr' [-Wvla]

Link: http://lkml.kernel.org/r/20190113183210.56154-1-olof@lixom.net
Signed-off-by: Olof Johansson <olof@lixom.net>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Colin Ian King <colin.king@canonical.com>
Cc: Jinbum Park <jinb.park7@gmail.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>