We need this in order to export symbols to external libraries.
E.g Cadence library needs __vec_memset / __vec_memcpy.
Previous commit d9aed376d5 ("zephyr: rtos: Add __vec_memcpy /
__vec_memset") is not enough in the case of external libs.
Signed-off-by: Daniel Baluta <daniel.baluta@nxp.com>