bootimg.bbclass: fix settings for grub-efi.bbclass
Fixed:
- Found potential conflicted var LABELS ...
Set LABELS to "boot install" would build out broken images when build
vm + live together, use set_live_vm_vars() to fix the problem.
- Use ROOT and LABEL in boot-directdisk.bbclass and image-foo.bbclass,
they are not only used by syslinux.bbclass, but also grub-efi.bbclass,
add "SYSLINUX_" prefix would mislead users.
Signed-off-by: Robert Yang <liezhi.yang@windriver.com> Signed-off-by: Ross Burton <ross.burton@intel.com>
