Fix gitignore to exclude vendor
Fix gitignore to exclude vendor

* Build scripts install to ./vendor, after testing something locally via
  the officially supported method `git status` should still list a
  pristine repository.

fixes #5573

dotandbo/spree,dotandbo/spree,dotandbo/spree,dotandbo/spree,yomishra/pce,yomishra/pce,yomishra/pce