build2 is an open source, cross-platform toolchain for building and packaging C++ code. It includes a build system, package manager, and repository web interface. There is also cppget.org, a public repository of open source C++ packages.
From the announcement:
This release includes a number of new features in the build system (high fidelity builds, command line configuration overrides), package manager (support for dropping no longer necessary packages), and repository web interface (ability to run multiple instances, look and feel customizations).