Update prepublish

Author: 3y3

package.json

@@ -34,7 +34,8 @@
   "devDependencies": {
     "aws-sdk": "^2.1.8",
     "mocha": "^2.1.0",
-    "chai": "^1.10.0"
+    "chai": "^1.10.0",
+    "rimraf": "^2.4.4"
   },
   "scripts": {
     "preinstall": "node -e 'process.exit(0)'",

tools/prepublish.js

@@ -1,8 +1,11 @@
 if (process.env.CI) process.exit(0);
 
+var rimraf = require('rimraf');
 var extend = require('util')._extend;
 var gyp = require('node-pre-gyp');
 
+rimraf.sync('./build');
+
 var versions = ['0.10.0', '0.12.0', '4.0.0', '5.0.0'];
 var matrix = {
   x64: ['win32', 'linux', 'darwin'],