Tup - http://gittup.org/tup
Tup is a file-based build system for Linux, OSX, and Windows. It inputs a list of file changes and a directed acyclic graph (DAG), then processes the DAG to execute the appropriate commands required to update dependent files. Updates are performed with very little overhead since tup implements powerful build algorithms to avoid doing unnecessary work. This means you can stay focused on your project rather than on your build system.
Further information is found at http://gittup.org/tup