boot/syslinux: add an option to install a MBR blob

This MBR blob will look for an active partition, and boot the bootcode
present in that partition. This can be used to boot an extlinux-prepared
partition.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Thomas Lundquist <lists@zelow.no>
Cc: Frank Hunleth <fhunleth@troodon-software.com>
Tested-by: Frank Hunleth <fhunleth@troodon-software.com>
Tested-by: Romain Naour <romain.naour@openwide.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

boot/syslinux/Config.in

@@ -30,6 +30,14 @@ config BR2_TARGET_SYSLINUX_PXELINUX
 	  Install the legacy-BIOS 'pxelinux' image, to boot off
 	  the network using PXE.
 
+config BR2_TARGET_SYSLINUX_MBR
+	bool "mbr"
+	select BR2_TARGET_SYSLINUX_LEGACY_BIOS
+	help
+	  Install the legacy-BIOS 'mbr' image, to boot off a
+	  local MBR-partition (e.g. prepared with 'extlinux'
+	  or 'syslinux').
+
 config BR2_TARGET_SYSLINUX_EFI
 	bool "efi"
 	select BR2_PACKAGE_GNU_EFI

boot/syslinux/syslinux.mk

@@ -60,6 +60,7 @@ endef
 
 SYSLINUX_IMAGES-$(BR2_TARGET_SYSLINUX_ISOLINUX) += bios/core/isolinux.bin
 SYSLINUX_IMAGES-$(BR2_TARGET_SYSLINUX_PXELINUX) += bios/core/pxelinux.bin
+SYSLINUX_IMAGES-$(BR2_TARGET_SYSLINUX_MBR) += bios/mbr/mbr.bin
 SYSLINUX_IMAGES-$(BR2_TARGET_SYSLINUX_EFI) += $(SYSLINUX_EFI_BITS)/efi/syslinux.efi
 
 define SYSLINUX_INSTALL_IMAGES_CMDS