Add nexus_clear_eflash function
Additionally we use this function at the end of nexus_flash to reset the
board and boot from the just-flashed image
Change-Id: Ia1915a32a3dcfd08771757773ff8ed65e49ae572
This is the project containing all the top-level build targets of all the projects within the GoB to set up the environment and build the e2e artifacts.