Use path.join to find LAB.src.js (thanks eslint!)

Also hush errors in LABjs itself.

Author: gigabo

packages/react-server/core/util/LAB.src.js

@@ -2,6 +2,7 @@
     v2.0.3 (c) Kyle Simpson
     MIT License
 */
+/* eslint-disable */
 
 (function(global){
 	var _$LAB = global.$LAB,

packages/react-server/core/util/LABString.js

@@ -1,10 +1,13 @@
-var lab = require("fs").readFileSync(__dirname + "/LAB.src.js", "utf-8");
+const path = require("path");
+const {readFileSync} = require("fs");
+
+var lab = readFileSync(path.join(__dirname, "LAB.src.js"), "utf-8");
 
 // Don't need this.
 lab = lab.replace(/^"use strict";/, "");
 
 // Run with `DEBUG_LAB=true` to see its output in console.log.
-if (!process.env.DEBUG_LAB) {
+if (!process.env.DEBUG_LAB) { // eslint-disable-line
 
 	// This is exactly what @getify does to remove debug code.
 	// https://github.com/getify/LABjs/blob/master/BUILD.md