code: def load_standalone(self, jamfile_module, file):
          
          assert isinstance(jamfile_module, basestring)
          assert isinstance(file, basestring)
  
          self.used_projects[jamfile_module] = []
          bjam.call("load", jamfile_module, file)
          self.load_used_projects(jamfile_module)
docs: Loads 'file' as standalone project that has no location
          associated with it.  This is mostly useful for user-config.jam,
          which should be able to define targets, but although it has
          some location in filesystem, we do not want any build to
          happen in user's HOME, for example.
  
          The caller is required to never call this method twice on
          the same file.