DEV: Add option to precompile default multisite stylesheets

lib/tasks/assets.rake

@@ -50,9 +50,9 @@ task 'assets:precompile:css' => 'environment' do
     STDERR.puts "Start compiling CSS: #{Time.zone.now}"
 
     RailsMultisite::ConnectionManagement.each_connection do |db|
-      # Heroku precompiles assets before db migration, so tables may not exist.
-      # css will get precompiled during first request instead in that case.
+      next if ENV["PRECOMPILE_SHARED_MULTISITE_CSS"] == "1" && db != "default"
 
+      # css will get precompiled during first request if tables do not exist.
       if ActiveRecord::Base.connection.table_exists?(Theme.table_name)
         STDERR.puts "Compiling css for #{db} #{Time.zone.now}"
         begin