Linux make file：如何提前退出for循环并显示错误消息

I am setting up a makefile to run a test that involves diffing a list of generated files against their counterparts in a master directory. I can get the loop to work and to exit if the diff fails but I haven't figured out how to include a failure message and still exit the for loop (and the make process) immediately.I am setting up a makefile to run a test that i