hack: use chokidar@2 only on node < 8 (#11560)

packages/babel-cli/package.json

@@ -33,7 +33,8 @@
     "source-map": "^0.5.0"
   },
   "optionalDependencies": {
-    "chokidar": "^2.1.8"
+    "chokidar": "^3.4.0",
+    "chokidarAt2": "https://registry.npmjs.org/chokidar/-/chokidar-2.1.8.tgz"
   },
   "peerDependencies": {
     "@babel/core": "^7.0.0-0"

packages/babel-cli/src/babel/util.js

@@ -116,7 +116,10 @@ process.on("uncaughtException", function (err) {
 
 export function requireChokidar(): Object {
   try {
-    return require("chokidar");
+    // todo(babel 8): revert `chokidarAt2` hack
+    return parseInt(process.version) >= 8
+      ? require("chokidar")
+      : require("chokidarAt2");
   } catch (err) {
     console.error(
       "The optional dependency chokidar failed to install and is required for " +