What is the best way to build C/C++ program in open source community?

We have a very old and big project which is mainly written by C (and a small piece of C++), and it can be built in both Linux and Windows. Currently, we write all the Makefiles in this project manually which I think is not good.

Now we want to make this project fully open source. However, before that, we want to enhance the way to build this project. So I'd like to know what is the best/popular way in open source community to build such project? I know a bit about autoconf/antomake which seems existing there for quit a long time, just wondering if any new and better way to build C/C+= project come up?

Thanks!