POST Make: fix the sub-dir dependencies missing.

Signed-off-by: Yuri Tikhonov <yur@emcraft.com>
diff --git a/post/Makefile b/post/Makefile
index a402e6a..666a896 100644
--- a/post/Makefile
+++ b/post/Makefile
@@ -45,7 +45,12 @@
 OBJS	:= $(addprefix $(obj),$(COBJS))
 LIB	:= $(obj)$(LIB)
 
-all:	$(LIB)
+all:	postdeps $(LIB)
+
+postdeps:
+	@for lib in $(SPLIB-y) ; do \
+		$(MAKE) -C `dirname $$lib` all ; \
+	done
 
 # generic POST library
 $(GPLIB): $(obj).depend $(OBJS)