fix(@ngtools/webpack): fix aot builds using npm packages that have lazy loaded modules

Currently, code splitting derived from routes with the loadChildren property only works if the resolved source file is a *.ts file in the source directory of your angular-cli project. If your project uses an npm package that has a route with loadChildren, the build will resolve the lazy loaded module as a *.d.ts definition file and then attempt to find an *.d.ts.ngfactory.ts file in the generated AOT directory, which does not exist. This fixes the path generation logic so the build will look for a *.ngfactory.ts file in $$_gendir/node_modules. Closes #5594

Author: maleetz

packages/@ngtools/webpack/src/plugin.ts

@@ -512,7 +512,8 @@ export class AotPlugin implements Tapable {
  if (this.skipCodeGeneration) {
  this._lazyRoutes[k] = lazyRoute;
  } else {
- const lr = path.relative(this.basePath, lazyRoute.replace(/\.ts$/, '.ngfactory.ts'));
+ const factoryPath = lazyRoute.replace(/(\.d)?\.ts$/, '.ngfactory.ts');
+ const lr = path.relative(this.basePath, factoryPath);
  this._lazyRoutes[k + '.ngfactory'] = path.join(this.genDir, lr);
  }
  });