[U-Boot] Makefile question

I am creating a file called config.tmp in my board specific folder within nand_spl during the configuration of my board in the top level Makefile. This is not a problem, however when I run make distclean this file still remains.

Perhaps I should not do this task in this manner. Based on the configuration for my board, I am defining PAD_TO to be either a large page NAND value or a small page value. Is there some other manner in which I should do this?

Ron