Support for newer grub-common package.

A recent change in grub-common package (#584415) has mandated
the use of a destination format in calls to grub-mkimage, a
parameter that was not previously supported.

scripts/build/lb_binary_iso

@@ -163,7 +163,14 @@ input_dir=/usr/lib/grub/i386-pc
 
 # build core.img
 core_img=\$(mktemp)
-grub-mkimage -d \${input_dir} -o \${core_img} biosdisk iso9660
+
+# first version requiring -O is 1.98+20100527, see #584415
+if [ "$(grub-mkimage --help | grep '\-O')" ]
+then
+	grub-mkimage -d \${input_dir} -o \${core_img} -O i386-pc biosdisk iso9660
+else
+	grub-mkimage -d \${input_dir} -o \${core_img} biosdisk iso9660
+fi
 
 # build grub_eltorito image
 cat \${input_dir}/cdboot.img \${core_img} > binary/boot/grub/grub_eltorito