libpayload: arm: Add EABI compatible utility functions.

Some EABI conformant toolchains like GCC need additional functions like raise.
To prevent payloads adding arch-specific implementations everywhere, we should
provide the default version in libpayload.

BUG=none
TEST=emerge-nyan libpayload # pass
BRANCH=none

Original-Change-Id: Id1e3c29590aa5881aefd944a7551949ce9a47b8f
Original-Signed-off-by: Hung-Te Lin <hungte@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/199686
(cherry picked from commit 395810c4b744dbb720050f79a2c1a30e81464554)
Signed-off-by: Marc Jones <marc.jones@se-eng.com>

Change-Id: I2e1d8c8cb519f8e788c22d081132d23b49b8f822
Reviewed-on: http://review.coreboot.org/7906
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

payloads/libpayload/arch/arm/Makefile.inc

@@ -31,6 +31,7 @@ CFLAGS += -mthumb -march=armv7-a
 arm_asm_flags = -Wa,-mthumb -Wa,-mimplicit-it=always -Wa,-mno-warn-deprecated
 
 head.o-y += head.S
+libc-y += eabi_compat.c
 libc-y += main.c sysinfo.c
 libc-y += timer.c coreboot.c util.S
 libc-y += virtual.c