The build2 toolchain requires Mac OS version 10.5 (Leopard) or later. We will
also be using the system C++ toolchain that comes with the Xcode Command Line
Tools. You should be able to use other/custom C++ toolchains, however, this is
the only configuration that is tested and guaranteed to work.

To verify that Command Line Tools are installed, run:

$ clang++ --version

It should produce something along these lines:

Apple LLVM version X.Y.Z (clang-A.B.C) (based on LLVM M.N.P)

To install Command Line Tools, run:

$ xcode-select --install

Once this is done continue with Bootstrapping on UNIX (BOOTSTRAP-UNIX file).
