Makefile: Add CONFIG_BUILD_TARGET to automatically build an special image

Add target to build it automatically upon "make" / MAKEALL. This can/should
be set by board / cpu specific headers if a special U-Boot image is
required for this SoC / board.

E.g. used by Marvell Armada XP to automatically build the u-boot.kwb
target.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Masahiro Yamada <yamada.m@jp.panasonic.com>

Makefile

@@ -758,6 +758,11 @@ endif
 endif
 endif
 
+# Add optional build target if defined in board/cpu/soc headers
+ifneq ($(CONFIG_BUILD_TARGET),)
+ALL-y += $(CONFIG_BUILD_TARGET:"%"=%)
+endif
+
 LDFLAGS_u-boot += $(LDFLAGS_FINAL)
 ifneq ($(CONFIG_SYS_TEXT_BASE),)
 LDFLAGS_u-boot += -Ttext $(CONFIG_SYS_TEXT_BASE)

README

@@ -2722,6 +2722,14 @@ CBFS (Coreboot Filesystem) support
 		200 ms.
 
 - Configuration Management:
+		CONFIG_BUILD_TARGET
+
+		Some SoCs need special image types (e.g. U-Boot binary
+		with a special header) as build targets. By defining
+		CONFIG_BUILD_TARGET in the SoC / board header, this
+		special image will be automatically built upon calling
+		make / MAKEALL.
+
 		CONFIG_IDENT_STRING
 
 		If defined, this string will be added to the U-Boot