checking git untracked files in CI

Reason for this MR: ICON buildbot checks for any untracked files created after make check. The command checking untracked files is located at scripts/buildbot_scripts/build_checks/check_git_untracked.sh

In this MR,

• gitignore is updated;
• YAXT gitlab CI is updated to check untracked files;
• files created during YAXT gitlab CI are excluded.