Enable purging when --purge option is supplied in CLI (#4772)

Do not require NODE_ENV to be set to 'production' as well, as using
the --purge option in the CLI should be explicit enough.

Co-authored-by: Arnout Roemers <roemers@zorgdomein.nl>

src/cli.js

@@ -420,7 +420,10 @@ async function build() {
     let resolvedConfig = resolveConfigInternal(config)
 
     if (args['--purge']) {
-      resolvedConfig.purge = args['--purge'].split(/(?<!{[^}]+),/)
+      resolvedConfig.purge = {
+        enabled: true,
+        content: args['--purge'].split(/(?<!{[^}]+),/),
+      }
     }
 
     if (args['--jit']) {