Use coreboot build system for libpayload, too.

This change makes building coreboot related projects more unified.

Change-Id: I0f1181e2fffde1e03675523f7dc9eef3119052c3
Signed-off-by: Patrick Georgi <patrick@georgi-clan.de>
Reviewed-on: http://review.coreboot.org/71
Tested-by: build bot (Jenkins)
Reviewed-by: Uwe Hermann <uwe@hermann-uwe.de>
diff --git a/payloads/libpayload/arch/i386/Makefile.inc b/payloads/libpayload/arch/i386/Makefile.inc
index 6461b72..2be5e54 100644
--- a/payloads/libpayload/arch/i386/Makefile.inc
+++ b/payloads/libpayload/arch/i386/Makefile.inc
@@ -27,9 +27,10 @@
 ## SUCH DAMAGE.
 ##
 
-TARGETS-y += arch/i386/head.S.o arch/i386/main.o arch/i386/sysinfo.o
-TARGETS-y += arch/i386/timer.o arch/i386/coreboot.o arch/i386/util.S.o
-TARGETS-y += arch/i386/exec.S.o arch/i386/virtual.o
+head.o-y += head.S
+libc-y += main.c sysinfo.c
+libc-y += timer.c coreboot.c util.S
+libc-y += exec.S virtual.c
 
 # Multiboot support is configurable
-TARGETS-$(CONFIG_MULTIBOOT) += arch/i386/multiboot.o
+libc-$(CONFIG_MULTIBOOT) += multiboot.c