Determining the OS & processor in make?

I'm wondering if there is a platform independent way to determine the OS & processor type that a Makefile is running on?

Using $(shell uname -a) would work fine on every UNIX system that I know of, but not on Windows.
Is there anything built into Make that tells you the OS & processor type?

But then you've also got to figure the different versions of the make program which is interpreting your makefile.

I think makefiles pretty much rely on configure scripts for this stuff, so nobody ever bothered to add OS identification.