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 major new features in the build system (support for Windows/MSVC, C compilation,
pkg-config integration, library versioning and export model, as well as the
uninstall operation) and packag manager (support for repository authentication and system packages).
This version has been tested on Windows, Linux, Mac OS, and FreeBSD with GCC, Clang (both vanilla and Apple's), MinGW GCC, MSVC, and Intel icc.