Add PRERENDER env var (#625)

* Add env.ssr

* Define PRERENDER env var.

Author: developit

src/lib/webpack/webpack-base-config.js

@@ -204,7 +204,8 @@ export default function (env) {
 		plugins: [
 			new webpack.NoEmitOnErrorsPlugin(),
 			new webpack.DefinePlugin({
-				'process.env.NODE_ENV': JSON.stringify(isProd ? 'production' : 'development')
+				'process.env.NODE_ENV': JSON.stringify(isProd ? 'production' : 'development'),
+				'PRERENDER': env.ssr ? 'true' : 'false'
 			}),
 			// Extract CSS
 			new ExtractTextPlugin({

src/lib/webpack/webpack-server-config.js

@@ -24,6 +24,7 @@ function serverConfig(env) {
 }
 
 export default function (env) {
+	env = Object.assign({}, env, { ssr: true });
 	return merge(
 		baseConfig(env),
 		serverConfig(env)