fix: create IPC channel for spawned babel-node process (#12836)

packages/babel-node/src/babel-node.js

@@ -81,7 +81,7 @@ getV8Flags(function (err, v8Flags) {
 
     const child_process = require("child_process");
     const proc = child_process.spawn(process.argv[0], args, {
-      stdio: "inherit",
+      stdio: ["inherit", "inherit", "inherit", "ipc"],
     });
     proc.on("exit", function (code, signal) {
       process.on("exit", function () {

packages/babel-node/test/fixtures/babel-node/subprocess-send/in-files/payload.js

@@ -0,0 +1,2 @@
+process.send({ hello: "world" });
+console.log("sent");

packages/babel-node/test/fixtures/babel-node/subprocess-send/options.json

@@ -0,0 +1,4 @@
+{
+  "args": ["payload.js"],
+  "stdout": "sent"
+}