strace: rename aarch64 target to arm64

Rename aarch64 build targets to arm64.  The gcc toolchain is still
aarch64.

Change-Id: Ia92d8a50824e5329cf00fd6f4f92eae112b7f3a3
diff --git a/Android.mk b/Android.mk
index 1459343..8d35756 100644
--- a/Android.mk
+++ b/Android.mk
@@ -116,12 +116,13 @@
 endif
 
 arch := $(TARGET_ARCH)
-ifeq ($(TARGET_ARCH),aarch64)
-    LOCAL_CFLAGS += -DAARCH64=1
-else ifeq ($(TARGET_ARCH),arm)
+ifeq ($(TARGET_ARCH),arm)
     LOCAL_CFLAGS += -DARM=1
     LOCAL_CFLAGS += -DHAVE_STAT64=1
     LOCAL_CFLAGS += -DHAVE_STRUCT___OLD_KERNEL_STAT=1
+else ($(TARGET_ARCH),arm64)
+    LOCAL_CFLAGS += -DAARCH64=1
+    arch := aarch64
 else ifeq ($(TARGET_ARCH),mips)
     LOCAL_CFLAGS += -DMIPS=1
     LOCAL_CFLAGS += -DHAVE_STAT64=1