A host dependency to xxd is required if the U-Boot board
configuration has CONFIG_USE_DEFAULT_ENV_FILE enabled. So
introduce a new BR U-Boot config option BR2_TARGET_UBOOT_NEEDS_XXD
to solve this problem. xxd is provided by host-vim.
Signed-off-by: Jerry Kooyman <jerry.kooyman@entrust.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>