Do not browserify xterm again inside search addon.
const buffer = require('vinyl-buffer');
const coveralls = require('gulp-coveralls');
const fs = require('fs-extra');
+const path = require('path');
const gulp = require('gulp');
const istanbul = require('gulp-istanbul');
const merge = require('merge-stream');
packageCache: {}
};
let searchBundle = browserify(searchOptions)
+ .external(path.join(outDir, 'xterm.js'))
.bundle()
.pipe(source('./addons/search/search.js'))
.pipe(buffer())