In autopkgtest, lib directory is renamed so gemspec can't work

--- a/Gemfile
+++ b/Gemfile
@@ -1,3 +1,8 @@
 source "https://rubygems.org"
 
-gemspec
+if ENV['AUTOPKGTEST_TMP']
+  gem 'scientist'
+  gem 'minitest'
+else
+  gemspec
+end