fix(@angular/cli): use rxjs path mapping helper in ejected config

Author: clydin

packages/@angular/cli/tasks/eject.ts

@@ -286,8 +286,10 @@ class JsonWebpackSerializer {
   }
 
   private _resolveReplacer(value: any) {
+    this.variableImports['rxjs/_esm5/path-mapping'] = 'rxPaths';
     return Object.assign({}, value, {
-      modules: value.modules.map((x: string) => './' + path.relative(this._root, x))
+      modules: value.modules.map((x: string) => './' + path.relative(this._root, x)),
+      alias: this._escape('rxPaths()')
     });
   }