add small delay on exit from babel

(cherry picked from commit 11961f7)

Author: jamestalmage

lib/babel.js

@@ -62,7 +62,9 @@ process.on('message', function (message) {
 });
 
 process.on('ava-kill', function () {
-	process.exit(0);
+	setTimeout(function () {
+		process.exit(0);
+	}, process.env.APPVEYOR ? 100 : 0);
 });
 
 process.on('ava-cleanup', function () {