This is not Zephyr related, it all depends on the bootloader you are using.
QMSI 1.1 had a bootloader that booted the sensor subsystem directly, not sure if this is still the case in recent releases though.
From: Singh, Rahul [mailto:rahul.singh(a)intel.com]
Sent: Wednesday, October 26, 2016 4:40 AM
Subject: [devel] Quark SE : x86 binary is always required for ARC to boot ?
Can anyone please confirm if the x86 binary is mandatory to flash on the board to boot the ARC or is there any configuration we need to add to build the ARC binary without flashing the x86 binary on the board.