The Requirements to build dotnet/runtime on Windows document lists a few external tools (namely CMake, Ninja and Python) that needs to be downloaded, installed and their executable added to the default PATH environment variable - but all these tools are already parts of the Visual Studio Community 2019 (with sufficient/higher versions) and can be easily installed via Visual Studio Installer (which can be automated further in provided .vsconfig), thus making the build environment setup basically just one-step VS install.