Bug 963030 - AArch64 support for IPC. r=bsmedberg

ipc/chromium/src/build/build_config.h

@@ -102,6 +102,9 @@
 #elif defined(__alpha__)
 #define ARCH_CPU_ALPHA 1
 #define ARCH_CPU_64_BITS 1
+#elif defined(__aarch64__)
+#define ARCH_CPU_AARCH64 1
+#define ARCH_CPU_64_BITS 1
 #else
 #error Please add support for your architecture in build/build_config.h
 #endif