Implement hard-source-webpack-plugin (#5181)

Follow-up of #5176

Closes #5173 as it led to inconsistencies in DX.

build/webpack.js

@@ -20,6 +20,7 @@ import { ReactLoadablePlugin } from './webpack/plugins/react-loadable-plugin'
 import {SERVER_DIRECTORY, NEXT_PROJECT_ROOT, NEXT_PROJECT_ROOT_NODE_MODULES, NEXT_PROJECT_ROOT_DIST, DEFAULT_PAGES_DIR, REACT_LOADABLE_MANIFEST, CLIENT_STATIC_FILES_RUNTIME_WEBPACK, CLIENT_STATIC_FILES_RUNTIME_MAIN} from '../lib/constants'
 import AutoDllPlugin from 'autodll-webpack-plugin'
 import TerserPlugin from 'terser-webpack-plugin'
+import HardSourceWebpackPlugin from 'hard-source-webpack-plugin'
 
 // The externals config makes sure that
 // on the server side when modules are
@@ -235,6 +236,7 @@ export default async function getBaseWebpackConfig (dir: string, {dev = false, i
           resolve: resolveConfig
         }
       }),
+      new HardSourceWebpackPlugin(),
       // This plugin makes sure `output.filename` is used for entry chunks
       new ChunkNamesPlugin(),
       !isServer && new ReactLoadablePlugin({

package.json

@@ -86,6 +86,7 @@
     "fresh": "0.5.2",
     "friendly-errors-webpack-plugin": "1.7.0",
     "glob": "7.1.2",
+    "hard-source-webpack-plugin": "0.12.0",
     "hoist-non-react-statics": "2.5.5",
     "htmlescape": "1.1.1",
     "http-errors": "1.6.2",