PXA: Fix off-the-tree build problems

Signed-off-by: Marek Vasut <marek.vasut@gmail.com>
diff --git a/board/vpac270/Makefile b/board/vpac270/Makefile
index 0f3eacd..c6f4c7c 100644
--- a/board/vpac270/Makefile
+++ b/board/vpac270/Makefile
@@ -24,25 +24,29 @@
 
 include $(TOPDIR)/config.mk
 
-LIB	= lib$(BOARD).a
+LIB	= $(obj)lib$(BOARD).a
 
-OBJS	:= vpac270.o
+COBJS	:= vpac270.o
 SOBJS	:= lowlevel_init.o
 
-$(LIB):	$(OBJS) $(SOBJS)
-	$(AR) crv $@ $(OBJS) $(SOBJS)
+SRCS	:= $(SOBJS:.o=.S) $(COBJS:.o=.c)
+OBJS	:= $(addprefix $(obj),$(COBJS))
+SOBJS	:= $(addprefix $(obj),$(SOBJS))
+
+$(LIB):	$(obj).depend $(OBJS) $(SOBJS)
+	$(AR) $(ARFLAGS) $@ $(OBJS) $(SOBJS)
 
 clean:
 	rm -f $(SOBJS) $(OBJS)
 
 distclean:	clean
-	rm -f $(LIB) core *.bak .depend
+	rm -f $(LIB) core *.bak $(obj).depend
 
 #########################################################################
 
-.depend:	Makefile $(SOBJS:.o=.S) $(OBJS:.o=.c)
-		$(CC) -M $(CPPFLAGS) $(SOBJS:.o=.S) $(OBJS:.o=.c) > $@
+# defines $(obj).depend target
+include $(SRCTREE)/rules.mk
 
--include .depend
+sinclude $(obj).depend
 
 #########################################################################