Merge pull request #40215 from vlado/file_path_joining_in_generator

Uniform paths joining in the code generated by `rails new`

railties/lib/rails/generators/rails/app/templates/config/environments/development.rb.tt

@@ -16,7 +16,7 @@ Rails.application.configure do
 
   # Enable/disable caching. By default caching is disabled.
   # Run rails dev:cache to toggle caching.
-  if Rails.root.join('tmp', 'caching-dev.txt').exist?
+  if Rails.root.join('tmp/caching-dev.txt').exist?
     <%- unless options.api? -%>
     config.action_controller.perform_caching = true
     config.action_controller.enable_fragment_cache_logging = true