buildroot/board/minnowboard/post-build.sh

#!/bin/sh
# args from BR2_ROOTFS_POST_SCRIPT_ARGS
# $2    board name

cp -v board/minnowboard/grub-${2}.cfg ${BINARIES_DIR}/efi-part/EFI/BOOT/grub.cfg

# Add a console on tty1
grep -qE '^tty1::' ${TARGET_DIR}/etc/inittab || \
sed -i '/GENERIC_SERIAL/a\
tty1::respawn:/sbin/getty -L  tty1 0 vt100 # HDMI console' ${TARGET_DIR}/etc/inittab