misc(builder): tweak server config

lib/builder/webpack/server.mjs

@@ -36,7 +36,7 @@ export default class WebpackServerConfig extends BaseConfig {
     let config = super.config()
 
     // Config devtool
-    config.devtool = this.options.dev ? 'cheap-source-map' : false
+    config.devtool = 'cheap-source-map'
 
     Object.assign(config, {
       target: 'node',
@@ -50,7 +50,11 @@ export default class WebpackServerConfig extends BaseConfig {
         hints: false,
         maxAssetSize: Infinity
       },
-      externals: []
+      externals: [],
+      optimization: {
+        splitChunks: false,
+        minimizer: []
+      }
     })
 
     // https://webpack.js.org/configuration/externals/#externals