build: remove obsolete gulp build task (#27386)

PR Close #27386

tools/gulp-tasks/build.js

@@ -1,21 +0,0 @@
-/**
- * @license
- * Copyright Google Inc. All Rights Reserved.
- *
- * Use of this source code is governed by an MIT-style license that can be
- * found in the LICENSE file at https://angular.io/license
- */
-
-module.exports = {
-  // build everything and generate bundles
-  'all': (gulp) => (done) => execBuild(done),
-  // same as all without the bundling part - faster / lower memory usage
-  'no-bundle': (gulp) => (done) => execBuild(done, '--bundle=false'),
-};
-
-function execBuild(done, args = '') {
-  const path = require('path');
-  const childProcess = require('child_process');
-  // increase maxbuffer to address out of memory exception when running certain tasks
-  childProcess.exec(path.join(__dirname, `../../build.sh ${args}`), {maxBuffer: 300 * 1024}, done);
-}