kbuild: Stop immediately on error

This patch restores the previous behavior of stopping the build
immediately on error (unless the -k option is given to make)

Before this patch, we would do the echo command no matter if the
compile failed, thus returning success always.

(Jan Harkes)

Rules.make

@@ -380,5 +380,5 @@ endif
 if_changed = $(if $(strip $? \
 		          $(filter-out $($(1)),$(cmd_$(@F)))\
 			  $(filter-out $(cmd_$(@F)),$($(1)))),\
-	       @echo $($(1)); $($(1)); echo 'cmd_$(@F) := $($(1))' > $(@D)/.$(@F).cmd)
+	       @echo $($(1)) && $($(1)) && echo 'cmd_$@ := $($(1))' > $(@D)/.$(@F).cmd)