Fix running of all.sh on macOS
Fix running of all.sh on macOS

Was getting 'dd: unknown operand status'

Signed-off-by: Tom Cosgrove <c6e7a4d0c027d32c62bc9570c565a01587ef99be@arm.com>

ARMmbed/mbedtls,Mbed-TLS/mbedtls,Mbed-TLS/mbedtls,ARMmbed/mbedtls,Mbed-TLS/mbedtls,ARMmbed/mbedtls,Mbed-TLS/mbedtls,ARMmbed/mbedtls