Add the Linux magic to the EFI file header to allow running our test
programs with GRUB's linux command.
MajorImageVersion = 1 indicates a kernel that can consume the
EFI_LOAD_FILE2_PROTOCOL. This allows to dump the GRUB provided intird with
our initrddump.efi tool.
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>