Another make for cross-platform builds is kmake (a part of kbuild, in its own words: kBuild is a makefile framework for writing simple makefiles for complex tasks.). It is an enhanced version of GNU make. It is developed by the VirtualBox folks. They use it to build their VirtualBox Product for Windows, Linux, MacOS and Solaris. Pretty portable!
See http://svn.netlabs.org/kbuild for details.
