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/cpu/mpc5xx/Makefile b/cpu/mpc5xx/Makefile
index b787b61..d696e79 100644
--- a/cpu/mpc5xx/Makefile
+++ b/cpu/mpc5xx/Makefile
@@ -1,4 +1,7 @@
 #
+# (C) Copyright 2006
+# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
+#
 # (C) Copyright 2003
 # Martin Winistoerfer, martinwinistoerfer@gmx.ch.
 #
@@ -32,21 +35,25 @@
 
 include $(TOPDIR)/config.mk
 
-LIB	= lib$(CPU).a
+LIB	= $(obj)lib$(CPU).a
 
-START	= start.S
-OBJS	= serial.o cpu.o cpu_init.o interrupts.o traps.o speed.o spi.o
+START	= start.o
+COBJS	= serial.o cpu.o cpu_init.o interrupts.o traps.o speed.o spi.o
 
-all:	.depend $(START) $(LIB)
+SRCS	:= $(START:.o=.S) $(SOBJS:.o=.S) $(COBJS:.o=.c)
+OBJS	:= $(addprefix $(obj),$(SOBJS) $(COBJS))
+START	:= $(addprefix $(obj),$(START))
+
+all:	$(obj).depend $(START) $(LIB)
 
 $(LIB):	$(OBJS)
 	$(AR) crv $@ $(OBJS)
 
 #########################################################################
 
-.depend:	Makefile $(START:.o=.S) $(OBJS:.o=.c)
-		$(CC) -M $(CFLAGS) $(START:.o=.S)  $(OBJS:.o=.c) > $@
+# defines $(obj).depend target
+include $(SRCTREE)/rules.mk
 
-sinclude .depend
+sinclude $(obj).depend
 
 #########################################################################