Three ways to get machine architecture

Two very common ways of getting the machine architecture are these: uname -m and arch. They both print things like x86_64. But I remember there is a third way to do that, but I can't remember what it was. I saw it some sort of Makefile-like script once, and for the love of god, I can't recall what it was. Does anyone remember what it was, and perhaps remember its use in build scripts? Thanks in advance -- this is kinda driving me a little crazy, tbh...