shellcheck_run_steps.py: read arch from pkg YAML

[AbduAzim424]

Read architecture from the package definition or default to x86_64 to prevent architecture specific packages to fail.

Example:

2025/08/05 19:16:32 ERRO error: skip this arch
Traceback (most recent call last):
  File "/home/runner/.cache/pre-commit/repogddl7mr3/py_env-python3.12/bin/shellcheck-run-steps", line 8, in <module>
    sys.exit(main())
             ^^^^^^
  File "/home/runner/.cache/pre-commit/repogddl7mr3/py_env-python3.12/lib/python3.12/site-packages/pre_commit_hooks/shellcheck_run_steps.py", line 112, in main
    subprocess.check_call(
  File "/usr/lib/python3.12/subprocess.py", line 413, in check_call
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['docker', 'run', '--volume=/home/runner/work/enterprise-packages/enterprise-packages:/work', '--rm', 'cgr.dev/chainguard/melange:latest', 'compile', '--arch=x86_64', '--pipeline-dir=./pipelines', 'raspberry-pi-utils.yaml']' returned non-zero exit status 1.
Unable to find image 'cgr.dev/chainguard/melange:latest' locally
latest: Pulling from chainguard/melange

raspberry-pi-utils.yaml package failed to pass the lint phase as we were using os.uname().machine of the CI environment for all the packages.

[dannf]

We can just look at the melange YAML and parse target-architectures. if that field exists, use the first arch it lists. If it doesn't exist, maybe just use x86_64.

[dannf]

thanks! I like this better. A few more comments inline.