Build legacy frontend in assets precompile, not postinstall

This would otherwise break on packager because bundle is not ready there

lib/tasks/assets.rake

@@ -48,12 +48,20 @@ namespace :assets do
   task :angular do
     OpenProject::Assets.clear!
 
+    puts "Building angular frontend"
     Dir.chdir Rails.root.join('frontend') do
       sh '$(npm bin)/ng build --prod' do |ok, res|
         raise "Failed to compile angular frontend: #{res.exitcode}" if !ok
       end
     end
 
+    puts "Building legacy frontend"
+    Dir.chdir Rails.root.join('frontend') do
+      sh 'npm run legacy-webpack' do |ok, res|
+        raise "Failed to compile angular frontend: #{res.exitcode}" if !ok
+      end
+    end
+
     puts "Writing angular assets manifest"
     OpenProject::Assets.rebuild_manifest!
   end