Netlify Webhook Codeload from different website

Postinstall.js

var shell = require('shelljs');
var fs = require('fs-extra');
var path = require('path');

console.log('WEBHOOK_BODY', process.env.WEBHOOK_BODY);

if (!shell.which('git')) {
  shell.echo('Sorry, this script requires git');
  shell.exit(1);
}

if (
  shell.exec(
    'curl https://codeload.github.com/jaredpalmer/formik/tar.gz/master | tar -xz --strip=0 formik-master/'
  ).code !== 0
) {
  shell.echo('Error: codeload failed');
  shell.exit(1);
}

shell.cd('formik-master/website');

// Use the latest version of Formik
const raw = fs.readFileSync(
  path.join(__dirname, './formik-master/website/package.json'),
  'utf8'
);

const pkg = JSON.parse(raw);
pkg.dependencies.formik = 'latest';

fs.writeJSONSync(
  path.join(__dirname, './formik-master/website/package.json'),
  pkg,
  null,
  2
);

// Use the latest version of Formik
const rawGatsbyConfig = fs.readFileSync(
  path.join(__dirname, './formik-master/website/gatsby-config.js'),
  'utf8'
);

const URL = process.env.DEPLOY_PRIME_URL
  ? process.env.DEPLOY_PRIME_URL
  : 'https://jaredpalmer.com';

// Alter Gatsby configuration so that final site knows it is being served on a
// path '/formik'
fs.writeFileSync(
  path.join(__dirname, './formik-master/website/gatsby-config.js'),
  rawGatsbyConfig.replace(
    `module.exports = {\n  siteMetadata: {\n`,
    `module.exports = {\n 
     pathPrefix: '/formik',
     siteMetadata: {
      siteUrl: '${URL}',
    `
  )
);

if (shell.exec('yarn').code !== 0) {
  shell.echo('Error: yarn install failure');
  shell.exit(1);
}

if (shell.exec('yarn deploy').code !== 0) {
  shell.echo('Error: yarn build failure');
  shell.exit(1);
}

if (shell.exec('mv public ../../dist').code !== 0) {
  shell.echo('Error: copy build');
  shell.exit(1);
}

shell.cd('..');
shell.cd('..');

if (shell.exec('mv ./dist ./public/formik').code !== 0) {
  shell.echo('Error: renaming formik directory');
  shell.exit(1);
}