# Create the group at compile time, so that you can have the gid available to
# pass to the user at creation
g = group "foo" do
  ...
end
g.run_action(:create)
provider = Chef::Platform.provider_for_node(node, g)
provider.load_current_resource
new_gid = provider.current_resource.gid

user "bob" do
  gid new_gid
end