libboost: fixed makefile

project/jni/boost/Android.mk

@@ -9,6 +9,10 @@ ifneq (boost,$(LOCAL_MODULE))
 LOCAL_C_INCLUDES := $(LOCAL_PATH)/include
 LOCAL_SRC_FILES := lib/$(TARGET_ARCH_ABI)/lib$(LOCAL_MODULE).a
 
+# NDK doesn't add the explicit dependency
+obj/local/$(TARGET_ARCH_ABI)/lib$(LOCAL_MODULE).a: $(LOCAL_PATH)/$(LOCAL_SRC_FILES)
+	cp -f $< $@
+
 include $(PREBUILT_STATIC_LIBRARY)
 
 endif