Add support for a saving build objects in a separate directory.
Modifications are based on the linux kernel approach and
support two use cases:

  1) Add O= to the make command line
  'make O=/tmp/build all'

  2) Set environement variable BUILD_DIR to point to the desired location
  'export BUILD_DIR=/tmp/build'
  'make'

The second approach can also be used with a MAKEALL script
'export BUILD_DIR=/tmp/build'
'./MAKEALL'

Command line 'O=' setting overrides BUILD_DIR environent variable.

When none of the above methods is used the local build is performed and
the object files are placed in the source directory.
diff --git a/board/omap2420h4/Makefile b/board/omap2420h4/Makefile
index ed47868..767a9d6 100644
--- a/board/omap2420h4/Makefile
+++ b/board/omap2420h4/Makefile
@@ -1,5 +1,5 @@
 #
-# (C) Copyright 2000, 2001, 2002
+# (C) Copyright 2000-2006
 # Wolfgang Denk, DENX Software Engineering, wd@denx.de.
 #
 # See file CREDITS for list of people who contributed to this
@@ -23,13 +23,17 @@
 
 include $(TOPDIR)/config.mk
 
-LIB	= lib$(BOARD).a
+LIB	= $(obj)lib$(BOARD).a
 
-OBJS	:= omap2420h4.o mem.o sys_info.o
+COBJS	:= omap2420h4.o mem.o sys_info.o
 SOBJS	:= lowlevel_init.o
 
-$(LIB):	$(OBJS) $(SOBJS)
-	$(AR) crv $@ $^
+SRCS	:= $(SOBJS:.o=.S) $(COBJS:.o=.c)
+OBJS	:= $(addprefix $(obj),$(COBJS))
+SOBJS	:= $(addprefix $(obj),$(SOBJS))
+
+$(LIB):	$(obj).depend $(OBJS) $(SOBJS)
+	$(AR) crv $@ $(OBJS) $(SOBJS)
 
 clean:
 	rm -f $(SOBJS) $(OBJS)
@@ -39,9 +43,9 @@
 
 #########################################################################
 
-.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
 
 #########################################################################