Allow engine variants other than "host_debug" to be clang-tidy linted

[jmagman]

Add a new --target-variant and --src-dir option to the clang-tidy linter script.
Update lint.sh to pass along the src-dir instead of the compile-commands path. The dart script will interpret this as src-dir/out/host_debug/compile_commands.json by default. Alternative --target-variant can be passed into the shell script.

$ ci/lint.sh --target-variant ios_debug

This will allow variants (is that the right word here?) other than host_debug to be run by the linter.

The recipe can then run the script for different targets
https://flutter.googlesource.com/recipes/+/refs/heads/main/recipes/engine_unopt.py#99
will become something like:

Lint(api, 'ios_debug_unopt')

def Lint(api, variant):
  checkout = GetCheckoutPath(api)
  with api.context(cwd=checkout):
    lint_cmd = checkout.join('flutter', 'ci', 'lint.sh', '--lint-all', '--target-variant', variant)
    api.step(api.test_utils.test_step_name('lint test'), [lint_cmd])

Note: in the future when the recipe is updated to use --target-variant, any outstanding PRs older than this script change will fail until merged in/rebased. I don't think it will impact future releases since they are versioned (will a beta release without this change run with that recipe? @christopherfujino )

Git pre-push hook continues to pass in --compile-commands and still works.

Other improvements:

• --format-style=file to use .clang-format file for fixes.
• Show all linter errors, not just the first one found.
• Remove the --repo option, calculate that directory relative to the script path.

flutter/flutter#61661

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read and followed the Flutter Style Guide and the C++, Objective-C, Java style guides.
• I listed at least one issue that this PR fixes in the description above.
• I added new tests to check the change I am making or feature I am adding, or Hixie said the PR is test-exempt. See testing the engine for instructions on
  writing and running engine tests.
• I updated/added relevant documentation (doc comments with ///).
• I signed the CLA.
• All existing and new tests are passing.

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[zanderso]

If you're computing this here, maybe we don't need the --repo command line argument anymore. Or the other way around, if you have the --repo argument, this is just the parent directory of that, right?

[jmagman]

Was there any case where --repo needs to handle some other repo directory? I wasn't sure why it was passed in in the first place.

[zanderso]

This pattern is probably safe here since we're always running the script from source, but it would break if the script were compiled to a snapshot and then the snapshot moved somewhere else before being run.

We can keep this and get rid of the --repo argument if that is simpler.

[jmagman]

it would break if the script were compiled to a snapshot and then the snapshot moved somewhere else before being run.

If you do that and it doesn't work: Give The Script A Break 🙂

[jmagman]

Removed --repo.

[jmagman]

Updated to remove this block. It was only showing the first file linter errors because a linter failure makes the process fail, which populates the job.exception, and breaks so doesn't show the other job failures.

[zanderso]

Nice catch

[zanderso]

This pattern is probably safe here since we're always running the script from source, but it would break if the script were compiled to a snapshot and then the snapshot moved somewhere else before being run.

We can keep this and get rid of the --repo argument if that is simpler.

[christopherfujino]

this shouldn't be an issue for beta branches, provided the engine builds were passing at the time the branch was made.