Add armv8-a arch variant

Change-Id: I7f6655f52068568e699fcd0f2a16202254cd3786
diff --git a/common/arch.go b/common/arch.go
index e524dd5..52c8347 100644
--- a/common/arch.go
+++ b/common/arch.go
@@ -141,6 +141,9 @@
 		Krait          interface{} `blueprint:"filter(android:\"arch_variant\")"`
 		Denver         interface{} `blueprint:"filter(android:\"arch_variant\")"`
 
+		// Arm64 arch variants
+		Armv8_a interface{} `blueprint:"filter(android:\"arch_variant\")"`
+
 		// Arm64 cpu variants
 		Cortex_a53_64 interface{} `blueprint:"filter(android:\"arch_variant\")"`
 		Denver64      interface{} `blueprint:"filter(android:\"arch_variant\")"`