nix is starting to replace all my build tools, building c code is as easy as putting together a small nix file like this: https://github.com/jb55/polyadvent/blob/master/default.nix

The nixpkgs community is then responsible for making sure that the build compiles on all platforms. It's not just for C code either, nix files can be used to declare any kind of dependency. It's a full blown declarative, functional, domain specific programming language for packages. So your project can depend on haskell or python code and everything just works.

There's a heavy linux focus right now but there's a whole group of people making the packages work nicely on osx and cygwin. Check it out: http://nixos.org/nix/