Files in build-aux

[Alan Third]

For a little while now I've had two files that seem to be updated when
I run make, and then git tells me have been modified:

build-aux/config.guess
build-aux/config.sub

I've just been resetting as and when required, but they always come
back after a build. I only see this on my mac, I don't see it on a
Debian system. Is there something I should be doing with them?
-- 
Alan Third