fix(@angular-devkit/build-angular): sockPath for custom path

Set devServer.sockPath to connect to reloading socket
via custom path when serving the app on a custom path.

Author: micmro

packages/angular_devkit/build_angular/src/dev-server/index.ts

@@ -423,6 +423,10 @@ function _addLiveReload(
   if (clientAddress.pathname) {
     clientAddress.pathname = path.posix.join(clientAddress.pathname, 'sockjs-node');
     sockjsPath = '&sockPath=' + clientAddress.pathname;
+    // ensure webpack-dev-server uses the correct path to connect to the reloading socket
+    if (webpackConfig.devServer) {
+      webpackConfig.devServer.sockPath = clientAddress.pathname;
+    }
   }
 
   const entryPoints = [`${webpackDevServerPath}?${url.format(clientAddress)}${sockjsPath}`];