Update to efivar 35
    fixes for older compilers
    efi_get_variable_exists()
    Lots of stuff to make CI work.
    use usleep() to avoid hitting the kernel rate limiter on efivarfs
    better EFI_GUID macro
    add efi_guid_fwupdate (0abba7dc-e516-4167-bbf5-4d9d1c739416)
    
    Signed-off-by: Peter Jones <pjones@redhat.com>