fix(build): Remove duplicate System declarations (#10713)

Add it to a common .d.ts. Prevents closure from complaining of duplicate declarations when compiled using tsickle to generate externs.

modules/@angular/core/src/linker/system_js_ng_module_factory_loader.ts

@@ -13,8 +13,6 @@ import {Compiler} from './compiler';
 import {NgModuleFactory} from './ng_module_factory';
 import {NgModuleFactoryLoader} from './ng_module_factory_loader';
 
-declare var System: {import: (module: string) => Promise<any>;};
-
 const _SEPARATOR = '#';
 
 const FACTORY_MODULE_SUFFIX = '.ngfactory';

modules/@angular/core/src/linker/systemjs_component_resolver.ts

@@ -13,8 +13,6 @@ import {Type} from '../type';
 import {ComponentFactory} from './component_factory';
 import {ComponentResolver} from './component_resolver';
 
-declare var System: {import: (module: string) => Promise<any>;};
-
 const _SEPARATOR = '#';
 
 /**

modules/@angular/core/tsconfig-es2015.json

@@ -18,6 +18,7 @@
   "files": [
     "index.ts",
     "testing.ts",
-    "../../../node_modules/zone.js/dist/zone.js.d.ts"
+    "../../../node_modules/zone.js/dist/zone.js.d.ts",
+    "../../system.d.ts"
   ]
 }

modules/@angular/core/tsconfig-es5.json

@@ -19,6 +19,7 @@
   "files": [
     "index.ts",
     "testing.ts",
-    "../../../node_modules/zone.js/dist/zone.js.d.ts"
+    "../../../node_modules/zone.js/dist/zone.js.d.ts",
+    "../../system.d.ts"
   ]
 }

modules/playground/src/bootstrap.ts

@@ -6,8 +6,6 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-declare var System: any;
-
 
 (function(global: any /** TODO #9100 */) {
 

modules/system.d.ts

@@ -0,0 +1,4 @@
+/**
+ * Dummy typings for systemjs.
+ */
+declare var System: any;

modules/types.d.ts

@@ -15,3 +15,4 @@
 /// <reference path="../node_modules/@types/protractor/index.d.ts" />
 /// <reference path="../node_modules/@types/selenium-webdriver/index.d.ts" />
 /// <reference path="./es6-subset.d.ts" />
+/// <reference path="./system.d.ts" />