The `tests/posix/headers/portability.posix.headers.without_posix_api`
test fails to build in case of toolchain which uses minimal libc by
default (for example ARC MWDT toolchain).
It can be easily fixed by providing sighal.h handler in minimal libc
Signed-off-by: Evgeniy Paltsev <PaltsevEvgeniy@gmail.com>
Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
