link atomic library. seems to be required in the latest Android NDK

java/jni/Android.mk

@@ -5,7 +5,7 @@ include $(CLEAR_VARS)
 LOCAL_MODULE := ZeroTierOneJNI
 LOCAL_C_INCLUDES := $(ZT1)/include
 LOCAL_C_INCLUDES += $(ZT1)/node
-LOCAL_LDLIBS := -llog
+LOCAL_LDLIBS := -llog -latomic
 # LOCAL_CFLAGS := -g
 
 # ZeroTierOne SDK source files