ARC: MWDT: explicitly forbid to use NEWLIB / NATIVE_APPLICATION

ARC MWDT doesn't support building Zephyr as an native
application (CONFIG_NATIVE_APPLICATION).
ARC MWDT doesn't support building with CONFIG_NEWLIB_LIBC
as it doesn't have newlib.

Let's explicitly forbid to use these Kconfig options for the
MWDT toolchain.

Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Signed-off-by: Evgeniy Paltsev <PaltsevEvgeniy@gmail.com>