Patch merged into filo/master: 1b31017 makefile: avoid unnecessary rebuilds

the following patch was just integrated into master:
commit 1b310177b04d265622ca220ce27f696b41fd786e
Author: Mathias Krause 
Date:   Tue Mar 6 13:14:47 2012 +0100

makefile: avoid unnecessary rebuilds

The make target libpayload is a phony target which makes filo and all
    the object files get rebuild on every make invokation. Avoid this by
    lifting the dependencies and rebuild, i.e. relink filo only when
    libpayload has changed.

Also, when building libpayload as a prerequisite, use $(obj) as DESTDIR,
    as the user might want to use a different build directory then $(src)/build.

Change-Id: Ifa42362ba1d8c88c9996d645314cfdbdf2994759
    Signed-off-by: Mathias Krause

Build-Tested: build bot (Jenkins) at Wed Mar  7 16:48:17 2012, giving +1
Reviewed-By: Stefan Reinauer  at Wed Mar  7 17:44:28 2012, giving +2
See http://review.coreboot.org/744 for details.

-gerrit