refactor(@angular-devkit/build-angular): set resolve roots to projectRoot

Previously roots was the same as context which was set to projectRoot, however in the previous change we changed the context to workspaceRoot.

With this change we maintain the same resolve root setting.

More info:
https://github.com/webpack/webpack/blob/4a3e4bda6b30915afd92f0b3c2aff5add149a635/lib/config/defaults.js#L875

 https://webpack.js.org/configuration/resolve/

Author: alan-agius4

packages/angular_devkit/build_angular/src/angular-cli-files/models/webpack-configs/common.ts

@@ -24,6 +24,7 @@ import {
   compilation,
   debug,
 } from 'webpack';
+import webpack = require('webpack');
 import { RawSource } from 'webpack-sources';
 import { AssetPatternClass } from '../../../browser/schema';
 import { BuildBrowserFeatures, maxWorkers } from '../../../utils';
@@ -471,13 +472,16 @@ export function getCommonConfig(wco: WebpackConfigOptions): Configuration {
     devtool: false,
     profile: buildOptions.statsJson,
     resolve: {
+      roots: [projectRoot],
       extensions: ['.ts', '.tsx', '.mjs', '.js'],
       symlinks: !buildOptions.preserveSymlinks,
       modules: [wco.tsConfig.options.baseUrl || projectRoot, 'node_modules'],
       plugins: [
         PnpWebpackPlugin,
       ],
-    },
+      // Cast since roots is currently not in typings
+      // See: https://github.com/DefinitelyTyped/DefinitelyTyped/pull/47233
+    } as webpack.Resolve,
     resolveLoader: {
       symlinks: !buildOptions.preserveSymlinks,
       modules: [