[CI] add simple .gitlab-ci

Modify app to return exit code when error happened.
1 job for add-flake in 60 minutes and 43 seconds (queued for 58 minutes and 6 seconds)
Status Job ID Name Coverage
  Test
failed #17686
cabal

01:00:43

 
Name Stage Failure
failed
cabal Test The script exceeded the maximum execution time set for the job
building '/nix/store/asjfgx5cjlx82yr88gk35rkwjpvwyiwi-unordered-containers-lib-unordered-containers-0.2.20.drv'...
building '/nix/store/3hhfzxmsr381p7rzgz1q8cp52jnyxkq9-mtl-lib-mtl-2.2.2.drv'...
building '/nix/store/k1hg66g6c63vh8hysbig44c2srlnwwl0-utf8-string-lib-utf8-string-1.0.2.drv'...
building '/nix/store/4p2nwdiwprzkzplhq8zs951v9yv0s1rd-happy-exe-happy-1.20.0.drv'...
building '/nix/store/i1prkz8fvbh24b8gf7y7f8jljm25053q-shake-lib-shake-0.19.8.drv'...
building '/nix/store/m6skkwfg4248ar5va7ziarsqghsxgj3r-hadrian-exe-hadrian-0.1.0.0.drv'...
building '/nix/store/hbignv65w69a4jmasxx0zbbshpbb934m-ghc-9.6.6.drv'...
WARNING: step_script could not run to completion because the timeout was exceeded. For more control over job and script timeouts see: https://docs.gitlab.com/ee/ci/runners/configure_runners.html#set-script-and-after_script-timeouts
ERROR: Job failed: execution took longer than 1h0m0s seconds