!5 删除lite_subsystem模板，使用原生的gn group内置函数

Merge pull request !5 from jady3356/master

BUILD.gn

@@ -11,16 +11,12 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import("//build/lite/config/subsystem/lite_subsystem.gni")
 import("//build/lite/config/component/lite_component.gni")
 
-lite_subsystem("iot") {
-    subsystem_components = [
-        ":link"
-    ]
+group("iot") {
+  deps = [ ":link" ]
 }
 
 lite_component("link") {
-    features = [
-    ]
+  features = []
 }