Fixed issue with default output options.

Author: Frank Schmid

lib/validate.js

@@ -102,16 +102,10 @@ module.exports = {
     // Default output
     if (!this.webpackConfig.output) {
       const outputPath = path.join(this.serverless.config.servicePath, '.webpack');
-      const outputFilename = path.basename(
-        _.isArray(this.webpackConfig.entry)
-        && this.webpackConfig.entry[this.webpackConfig.entry.length - 1]
-        || this.webpackConfig.entry
-        || 'handler.js'
-      );
       this.webpackConfig.output = {
         libraryTarget: 'commonjs',
         path: outputPath,
-        filename: outputFilename,
+        filename: '[name].js',
       };
     }