Fix Babel config file detection

Author: jdreesen

lib/config/parse-runtime.js

@@ -101,7 +101,7 @@ module.exports = function(argv, cwd) {
         cwd: cwd,
         filename: path.join(cwd, 'webpack.config.js')
     });
-    runtimeConfig.babelRcFileExists = (typeof partialConfig.babelrc === 'string');
+    runtimeConfig.babelRcFileExists = partialConfig.hasFilesystemConfig();
 
     return runtimeConfig;
 };