Babel transformations refactoring

Summary: Just a small refactoring to only create array with plugins once. This should make transformations a bit faster as all these methods are called many times for each file in the project.

Reviewed By: passy

Differential Revision: D21308498

fbshipit-source-id: 0ed47f13cebfebd2992817caa207dc55f1dbeb0a

desktop/scripts/jest-transform.js

@@ -7,16 +7,16 @@
  * @format
  */
 
-// eslint-disable-next-line import/no-unresolved
-const {transform} = require('../babel-transformer/lib/transform-jest');
 const isFB = require('./isFB');
 
 if (isFB && process.env.FLIPPER_FB === undefined) {
   process.env.FLIPPER_FB = 'true';
 }
-
 process.env.FLIPPER_TEST_RUNNER = 'true';
 
+// eslint-disable-next-line import/no-unresolved
+const {transform} = require('../babel-transformer/lib/transform-jest');
+
 module.exports = {
   process(src, filename, config, options) {
     return transform({