chore(build): Move broccoli support to own module.

Add support for multiple pipelines in different Brocfile's.

tools/broccoli/gulp/index.js

@@ -0,0 +1,52 @@
+var broccoli = require('broccoli');
+var copyDereferenceSync = require('copy-dereference').sync;
+var fse = require('fs-extra');
+var path = require('path');
+
+module.exports = broccoliBuild;
+var broccoliExecuted = {};
+
+/**
+ * Integration point to run a broccoli build pipeline under gulp.
+ * This is mostly derived from the broccoli-cli
+ * @param tree a broccoli tree, obtained by calling `require` on the Brocfile
+ * @param outputRoot the path under 'dist' owned exclusively by this Brocfile
+ * @returns the promise to return back to gulp
+ */
+function broccoliBuild(tree, outputRoot) {
+  if (broccoliExecuted.hasOwnProperty(outputRoot)) {
+    throw new Error('The broccoli task can be called only once for outputRoot ' + outputRoot);
+  }
+  broccoliExecuted[outputRoot] = true;
+
+  var distPath = path.join('dist', outputRoot);
+
+  // We do a clean build every time to avoid stale outputs.
+  // Broccoli's cache folders allow it to remain incremental without reading this dir.
+  fse.removeSync(distPath);
+  fse.mkdirsSync(path.join(distPath, '..'));
+
+  var builder = new broccoli.Builder(tree);
+  return builder.build()
+    .then(function (hash) {
+      var dir = hash.directory;
+      try {
+        copyDereferenceSync(path.join(dir, outputRoot), distPath);
+      } catch (err) {
+        if (err.code === 'EEXIST') err.message += ' (we cannot build into an existing directory)';
+        throw err;
+      }
+    })
+    .finally(function () {
+      builder.cleanup();
+    })
+    .catch(function (err) {
+      // Should show file and line/col if present
+      if (err.file) {
+        console.error('File: ' + err.file);
+      }
+      console.error(err.stack);
+      console.error('\nBuild failed');
+      process.exit(1);
+    });
+}