Change v8flags to use temp file instead of new process

Using npm's preinstall hook, this task it's very simple. Before installation of package, the file with flags will be created and fetch.js will use that file instead of spawning new process. It will limit black magic to none :)

fetch.js

@@ -1,18 +1,17 @@
 const fs = require('fs');
 const path = require('path');
 
-const exec = require('child_process').exec;
-const nodePath = process.execPath;
 const version = process.versions.v8;
 const tmpfile = path.join(__dirname, version+'.flags.json');
+const flagsFile = path.join(__dirname, 'flags.temp');
 
 if (!fs.existsSync(tmpfile)) {
-  exec('"'+nodePath+'" --v8-options', function (execErr, result) {
+  fs.readFile( flagsFile, function( execErr, result) {
     var flags;
     if (execErr) {
       throw new Error(execErr);
     } else {
-      flags = result.match(/\s\s--(\w+)/gm).map(function (match) {
+      flags = result.toString().match(/\s\s--(\w+)/gm).map(function (match) {
         return match.substring(2);
       });
       fs.writeFile(tmpfile, JSON.stringify(flags), { encoding:'utf8' },

package.json

@@ -21,6 +21,7 @@
     }
   ],
   "scripts": {
+    "preinstall": "node --v8-options >> flags.temp",
     "install": "node fetch.js",
     "test": "mocha -R spec test.js"
   },