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

Review URL: https://codereview.chromium.org/145273028

git-svn-id: http://src.chromium.org/svn/trunk/src/build@249246 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

build_config.h

@@ -106,6 +106,11 @@
 #define ARCH_CPU_ARMEL 1
 #define ARCH_CPU_32_BITS 1
 #define ARCH_CPU_LITTLE_ENDIAN 1
+#elif defined(__arm64__)
+#define ARCH_CPU_ARM_FAMILY 1
+#define ARCH_CPU_ARM64 1
+#define ARCH_CPU_64_BITS 1
+#define ARCH_CPU_LITTLE_ENDIAN 1
 #elif defined(__pnacl__)
 #define ARCH_CPU_32_BITS 1
 #define ARCH_CPU_LITTLE_ENDIAN 1