Retire LOCAL_NDK_VERSION.

Bug: 6932421
Change-Id: I77f71dc7bdfc8ab539be95ee23d9e24c0a298711
diff --git a/Android.mk b/Android.mk
index e62a069..cb4f6d7 100644
--- a/Android.mk
+++ b/Android.mk
@@ -62,7 +62,6 @@
 include $(CLEAR_VARS)
 
 ifeq ($(TARGET_ARCH),arm)
-LOCAL_NDK_VERSION := 4
 LOCAL_SDK_VERSION := 8
 endif
 
@@ -79,7 +78,6 @@
 include $(CLEAR_VARS)
 
 ifeq ($(TARGET_ARCH),arm)
-LOCAL_NDK_VERSION := 4
 LOCAL_SDK_VERSION := 8
 endif