fix GRUB config to add a HOS menu entry

Rsconscript

@@ -39,10 +39,12 @@ EOF
           end
           File.open("#{tmpdir}/ext2/grub.cfg", "wb") do |fh|
             fh.write(<<EOF)
-insmod part_gpt
-insmod multiboot
-set root=(hd0,gpt2)
-multiboot /hos.elf
+menuentry "HOS" {
+  insmod part_gpt
+  insmod multiboot
+  set root=(hd0,gpt2)
+  multiboot /hos.elf
+}
 EOF
           end
           system(*%W[genext2fs -b #{HOS_PART_SIZE * 1024} -d #{tmpdir}/ext2 #{tmpdir}/ext2.part])