Add ARMv8-A to the supported list of arm platforms

src/base/atomicops_internals_arm_gcc.h

Index: src/base/atomicops_internals_arm_gcc.h
diff --git a/src/base/atomicops_internals_arm_gcc.h b/src/base/atomicops_internals_arm_gcc.h
index e399657e13ca9a79b3632b074b026822c07b9e55..eb64f52b167f410282a89a75abf93609ce920570 100644
--- a/src/base/atomicops_internals_arm_gcc.h
+++ b/src/base/atomicops_internals_arm_gcc.h
@@ -59,7 +59,8 @@ inline void MemoryBarrier() {
 // variant of the target architecture is being used. This tests against
 // any known ARMv6 or ARMv7 variant, where it is possible to directly
 // use ldrex/strex instructions to implement fast atomic operations.
-#if defined(__ARM_ARCH_7__) || defined(__ARM_ARCH_7A__) ||  \
+#if defined(__ARM_ARCH_8A__) || \
+    defined(__ARM_ARCH_7__) || defined(__ARM_ARCH_7A__) ||  \
     defined(__ARM_ARCH_7R__) || defined(__ARM_ARCH_7M__) || \
     defined(__ARM_ARCH_6__) || defined(__ARM_ARCH_6J__) ||  \
     defined(__ARM_ARCH_6K__) || defined(__ARM_ARCH_6Z__) || \