add kernel-install tool for bootloader Spec

This adds a tool for installing kernels according to the bootloader
spec. systemd already has a similar tool, but it is limited to installing
kernels on the currently running system. The barebox kernel-install
tool instead can also be used to install kernels on removable media on a
development host for cross development. It is compiled in two variants,
as 'kernel-install' for the host and as 'kernel-install-target' using
$CROSS_COMPILE.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

common/Kconfig

@@ -451,6 +451,14 @@ config BLSPEC
 	  on a device and it allows the Operating System to install / update
 	  kernels.
 
+config KERNEL_INSTALL_TARGET
+	bool
+	prompt "Build kernel-install utility for the target"
+	help
+	  Enable this to compile the kernel-install script using the cross
+	  compiler. The utility for the target will be under
+	  scripts/kernel-install-target
+
 choice
 	prompt "console support"
 	default CONSOLE_FULL

scripts/Makefile

@@ -8,6 +8,7 @@ hostprogs-y                      += bin2c
 hostprogs-y                      += mkimage
 hostprogs-y                      += fix_size
 hostprogs-y                      += bareboxenv
+hostprogs-y                      += kernel-install
 hostprogs-$(CONFIG_KALLSYMS)     += kallsyms
 hostprogs-$(CONFIG_ARCH_MVEBU)   += kwbimage kwboot
 hostprogs-$(CONFIG_ARCH_NETX)    += gen_netx_image
@@ -24,6 +25,7 @@ subdir-$(CONFIG_X86)		+= setupmbr
 subdir-$(CONFIG_DTC)		+= dtc
 
 targetprogs-$(CONFIG_BAREBOXENV_TARGET) += bareboxenv-target
+targetprogs-$(CONFIG_KERNEL_INSTALL_TARGET) += bareboxenv-target
 
 # Let clean descend into subdirs
 subdir-	+= basic kconfig setupmbr