allow_failure:exit_codes unusable with windows shell executor because exit code is always 1

Summary

With the shell executor on windows, a job with a failing script line always exits with code 1 instead of the failing exit code. This bug does not occur if using the docker-windows executor.

This renders allow_failure exit_codes unusable if using the shell executor, because it is impossible to distinguish between types of failures.

Steps to reproduce

setup gitlab runner with shell executor (repros on revision=b37d3da9 version=14.3.0)
use the following .gitlab-ci.yml:

broken_job:
  script:
  - python -c "import sys;sys.exit(100)"
  # Or use: powershell { exit 100 }
  # Or use: exit 100
  allow_failure:
    exit_codes: 100

run the pipeline and see the job fail

Example Project

https://gitlab.com/ken.kania/exit-code-bug

Job should be allowed to fail, but instead fails: https://gitlab.com/ken.kania/exit-code-bug/-/pipelines/376260769

What is the current bug behavior?

An item in a job's script array that results in any nonzero exit code causes the job to exit with code 1.

What is the expected correct behavior?

An item in a job's script array that results in any nonzero exit code causes the job to exit with the corresponding exit code.

Relevant logs and/or screenshots

DEBUG:  219+  >>>> echo "`$ python -c `"import sys;sys.exit(100)`""
$ python -c "import sys;sys.exit(100)"
DEBUG:  220+  >>>> python -c "import sys;sys.exit(100)"
DEBUG:  221+ if( >>>> !$?) { Exit &{if($LASTEXITCODE) {$LASTEXITCODE} else {1}}
 }
DEBUG:  221+ if(!$?) {  >>>> Exit &{if($LASTEXITCODE) {$LASTEXITCODE} else {1}}
 }
DEBUG:  221+ if(!$?) { Exit  >>>> &{if($LASTEXITCODE) {$LASTEXITCODE} else {1}}
 }
DEBUG:  221+ if(!$?) { Exit & >>>> {if($LASTEXITCODE) {$LASTEXITCODE} else {1}}
 }
DEBUG:     ! CALL function '<ScriptBlock>'  (defined in file 
'C:\Windows\TEMP\build_script924156239\script.ps1')
DEBUG:  221+ if(!$?) { Exit &{if( >>>> $LASTEXITCODE) {$LASTEXITCODE} else {1}}
 }
DEBUG:  221+ if(!$?) { Exit &{if($LASTEXITCODE) { >>>> $LASTEXITCODE} else {1}}
 }
DEBUG:  221+ if(!$?) { Exit &{if($LASTEXITCODE) {$LASTEXITCODE} else {1} >>>> }
 }
...
ERROR: Job failed: exit status 1