Build tools: Build webpack dev in grunt build.

For the WordPress zip we need both the minified and non-minified files. This is because of `SCRIPT_DEBUG`. So in grunt build we need to do both `grunt webpack:prod` and `grunt webpack:dev`.

Props bordoni, atimmer.

Merges [43817] to trunk.

Fixes #45156.

git-svn-id: https://develop.svn.wordpress.org/trunk@44161 602fd350-edb4-49c9-b593-d223f7449a82

Gruntfile.js

@@ -1360,6 +1360,7 @@ module.exports = function(grunt) {
 		'includes:embed',
 		'usebanner',
 		'webpack:prod',
+		'webpack:dev',
 		'jsvalidate:build'
 	] );