imagebuilder: fix parallel building (closes #11117)

SVN-Revision: 30927

target/Makefile

@@ -10,7 +10,10 @@ $(curdir)/builddirs:=linux sdk imagebuilder toolchain
 $(curdir)/builddirs-default:=linux
 $(curdir)/builddirs-install:=linux $(if $(CONFIG_SDK),sdk) $(if $(CONFIG_IB),imagebuilder) $(if $(CONFIG_MAKE_TOOLCHAIN),toolchain)
 
-$(curdir)/imagebuilder/prepare:=$(curdir)/linux/install
+$(curdir)/imagebuilder/compile:=$(curdir)/linux/install
+
+# prerequisites for the individual targets
+$(curdir)//install = $(1)/compile
 
 $(eval $(call stampfile,$(curdir),target,prereq,.config))
 $(eval $(call stampfile,$(curdir),target,compile,$(TMP_DIR)/.build))