@classmethod<EOL><INDENT>def child_build_system(cls):<DEDENT>
return None<EOL>
Returns the child build system.

        Some build systems, such as cmake, don't build the source directly.
        Instead, they build an interim set of build scripts that are then
        consumed by a second build system (such as make). You should implement
        this method if that's the case.

        Returns:
            Name of build system (corresponding to the plugin name) if this
            system has a child system, or None otherwise.