grub, hdt: Add hdt support for grub-pc (memdisk + floppy image)

features.in/grub/cfg.in/90hdt_bios.cfg

+if [ "$grub_platform" = "pc" ]; then
+  menuentry "Hardware Info" {
+    linux16 /boot/memdisk
+    initrd16 /boot/hdt.img
+  }
+fi

features.in/hdt/config.mk

 # optimized out use/syslinux due to use/memtest
 ifeq (,$(filter-out i586 x86_64,$(ARCH)))
-use/hdt: use/memtest
+use/hdt: use/syslinux use/memtest
 	@$(call add_feature)
 	@$(call add,STAGE1_PACKAGES,pciids)
+	@$(call add,STAGE1_PACKAGES,dosfstools)
 	@$(call add,SYSLINUX_MODULES,hdt)
+	@$(call add,GRUB_CFG,hdt_bios)
+	@$(call set,GLOBAL_HSH_PROC,1)
 else
 use/hdt: ; @:
 endif

features.in/hdt/stage1/scripts.d/10-hdt-img

+#!/bin/sh -efu
+
+[ "$GLOBAL_BOOTLOADER" = grubpcboot ] || exit 0
+
+cd "$WORKDIR"
+
+mkdir -p boot syslinux
+cp /usr/lib/syslinux/hdt.c32 "$WORKDIR"/syslinux/
+
+cat > syslinux/syslinux.cfg << EOF
+default hdt
+label hdt
+  menu label ^Hardware info
+  com32 hdt.c32
+  append quiet
+EOF
+
+# floppy disk 720 KiB
+dd if=/dev/zero of=boot/hdt.img bs=512 count="1440"
+mkfs.fat -n HDT -F 12 boot/hdt.img
+mcopy -i boot/hdt.img -s syslinux ::
+
+#dd if=/usr/lib/syslinux/ldlinux.bss of=boot/hdt.img conv=notrunc
+syslinux -d /syslinux --install boot/hdt.img
+
+rm -r syslinux
+cp /usr/lib/syslinux/memdisk boot