upgrade code to webpack v5

Ref: https://webpack.js.org/migrate/5/

Author: bpinto

lib/build.js

@@ -158,12 +158,11 @@ async function webpackConfig(
     entry: {},
     target: 'node',
     plugins: [
-      new webpack.IgnorePlugin(/vertx/),
+      new webpack.IgnorePlugin({ resourceRegExp: /vertx/ }),
       new webpack.DefinePlugin(defineEnv),
     ],
     output: {
       path: functionsPath,
-      filename: '[name].js',
       libraryTarget: 'commonjs',
     },
     optimization: {

lib/build.spec.js

@@ -106,8 +106,6 @@ describe('build', () => {
     });
 
     describe('webpack custom config merge', () => {
-      beforeEach(() => jest.resetModules());
-
       it('should merge plugins', async () => {
         const script = `module.exports = () => console.log("hello world")`;
         await writeFileInFunctions(script, 'index.js');