Merge branch 'load-knapsack-if-defined' into 'master'

Load knapsack in Rakefile only when is bundled

Fixes `production` builds: https://dev.gitlab.org/gitlab/omnibus-gitlab/builds/85407

cc @marin 

See merge request !4514

Gemfile

@@ -308,6 +308,7 @@ group :development, :test do
   gem 'benchmark-ips', require: false
 
   gem "license_finder", require: false
+  gem 'knapsack'
 end
 
 group :test do
@@ -316,7 +317,6 @@ group :test do
   gem 'webmock', '~> 1.21.0'
   gem 'test_after_commit', '~> 0.4.2'
   gem 'sham_rack'
-  gem 'knapsack'
 end
 
 group :production do

Rakefile

@@ -3,11 +3,10 @@
 # for example lib/tasks/capistrano.rake, and they will automatically be available to Rake.
 
 require File.expand_path('../config/application', __FILE__)
-require 'knapsack'
 
 relative_url_conf = File.expand_path('../config/initializers/relative_url', __FILE__)
 require relative_url_conf if File.exist?("#{relative_url_conf}.rb")
 
 Gitlab::Application.load_tasks
 
-Knapsack.load_tasks
+Knapsack.load_tasks if defined?(Knapsack)