Fix compilation of base for arm64

Fix compilation of base for arm64

Add support for the architecture to build/build_config.h (define
new macro ARCH_CPU_ARM64 to identify the CPU architecture and
set the other appropriate macros to 1).

Fix DEBUG_BREAK_ASM() macro to expand to the correct instruction
on arm64 cpu (as instruction set is not compatible with previous
version of ARM instruction sets).

BUG=339477
R=mark@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=249246

[sdefresne, 2014-02-05 18:03:39]

PTAL

[Mark Mentovai, 2014-02-05 18:46:30]

LGTM assuming __ARMEL__ isn’t defined when targeting ARMv8 (64).

[sdefresne, 2014-02-05 21:47:35]

The CQ bit was checked by sdefresne@chromium.org

[commit-bot: I haz the power, 2014-02-05 21:49:48]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/sdefresne@chromium.org/145273028/1

[sdefresne, 2014-02-05 21:51:10]

On 2014/02/05 18:46:30, Mark Mentovai wrote:
> LGTM assuming __ARMEL__ isn’t defined when targeting ARMv8 (64).

AFAIK, __ARMEL__ is not defined when targeting ARMv8.

[commit-bot: I haz the power, 2014-02-06 02:51:06]

Change committed as 249246