https://gn.googlesource.com/gn/+/refs/heads/master/examples/simple_build/build
BSD 3-Clause
gn is metabuild system that generates ninja files for further compilation
gn tool requires paths to all the toolchains to be used for compilation, for example compiler, linker etc. The toolchains in toolchain/BUILD.gn are from the examples repository for gn. BUILDCONFIG.gn is also trimmed down version from examples/simple_build/build/