builds less files on request

build-less.js

var Promise = require('bluebird')
	, less    = Promise.promisifyAll(require('less'))
	, path    = require('path')
	, fs      = require('fs')
	, through = require('through2')

app.get('/node_modules/bootstrap/less/glyphicons.less', (req, res) => {
	res.header("Content-type", "text/css");

	fs.createReadStream(path.join(__dirname, './node_modules/bootstrap/less/glyphicons.less'))
		.pipe(
			through(function (chunk, end, cb) {
				this.push(`
					//** Load fonts from this directory.
					@icon-font-path: "/node_modules/bootstrap/fonts/";
					//** File name for all font files.
					@icon-font-name: "glyphicons-halflings-regular";
					//** Element ID within SVG icon file.
					@icon-font-svg-id: "glyphicons_halflingsregular";

					${chunk.toString('utf8')}
				`)
				cb()
			})
		)
		.pipe(
			through(function (chunk, enc, cb) {
				less.renderAsync(chunk.toString('utf8'))
					.then((compiled) => {
						this.push(compiled.css)
						cb()
					})
			})
		)
		.pipe(res)
})