Merge "Fix failure to copy data files if content changes"

libs.mk

@@ -395,7 +395,7 @@ libvpx_test_srcs.txt:
 	@echo $(LIBVPX_TEST_SRCS) | xargs -n1 echo | sort -u > $@
 CLEAN-OBJS += libvpx_test_srcs.txt
 
-$(LIBVPX_TEST_DATA):
+$(LIBVPX_TEST_DATA): $(SRC_PATH_BARE)/test/test-data.sha1
 	@echo "    [DOWNLOAD] $@"
 	$(qexec)trap 'rm -f $@' INT TERM &&\
             curl -L -o $@ $(call libvpx_test_data_url,$(@F))