refactor: add .buildtool/ and ci_utilities/ to .gitignore

Author: vboutrou

.gitignore

@@ -47,5 +47,7 @@ codegen/
 # Project settings
 Utilities/ProjectSettings.mat
 
-# GitLab page folder
-public/
+# Testing and CI related artifact
+public/
+.buildtool/
+ci_utilities/