Clang-tidy: Fixed math on shard-id validator.

[gaaclarke]

fixes failure: https://logs.chromium.org/logs/flutter/buildbucket/cr-buildbucket/8798099822610209889/+/u/test:_lint_host_debug/stdout

That resulted in revert: https://flutter-review.git.corp.google.com/c/recipes/+/35742

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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[gaaclarke]

Here is recipe reland: https://flutter-review.git.corp.google.com/c/recipes/+/35781

[cyanglaz]

LGTM

[auto-submit]

auto label is removed for flutter/engine, pr: 37433, due to - The status or check suite Linux Unopt has failed. Please fix the issues identified (or deflake) before re-applying this label.

[zanderso]

One of the new tests is failing.

[gaaclarke]

One of the new tests is failing.

Great, works locally. Digging in...

[gaaclarke]

Updated the tests to just operate on Options. There was some git command run by the tool that happened to work locally, but didn't remotely.

[auto-submit]

auto label is removed for flutter/engine, pr: 37433, due to - The status or check suite Mac Unopt has failed. Please fix the issues identified (or deflake) before re-applying this label.

[gaaclarke]

Looks like the test is being run on the bot with a non existent path for compile_commands.json:

Test "shard-id valid": Failed
In test "shard-id valid" Expect.isNull(actual: <ERROR: Build commands path /Volumes/Work/s/w/ir/cache/builder/src/out/host_debug/compile_commands.json doesn't exist.>) fails.
#0      Expect._fail (package:expect/expect.dart:698:5)
#1      Expect.isNull (package:expect/expect.dart:143:5)
#2      isNull (package:async_helper/async_minitest.dart:215:10)
#3      expect (package:async_helper/async_minitest.dart:70:4)
#4      main.<anonymous closure> (file:///Volumes/Work/s/w/ir/cache/builder/src/flutter/tools/clang_tidy/test/clang_tidy_test.dart:125:5)
#5      Test.run.<anonymous closure>.<anonymous closure> (package:litetest/src/test.dart:69:21)
#6      new Future.<anonymous closure> (dart:async/future.dart:253:37)
#7      _rootRun (dart:async/zone.dart:1390:47)
#8      _CustomZone.run (dart:async/zone.dart:1300:19)
#9      _CustomZone.runGuarded (dart:async/zone.dart:1208:7)
#10     _CustomZone.bindCallbackGuarded.<anonymous closure> (dart:async/zone.dart:1248:23)
#11     _rootRun (dart:async/zone.dart:1398:13)
#12     _CustomZone.run (dart:async/zone.dart:1300:19)
#13     _CustomZone.bindCallback.<anonymous closure> (dart:async/zone.dart:1232:23)
#14     Timer._createTimer.<anonymous closure> (dart:async-patch/timer_patch.dart:18:15)
#15     _Timer._runTimers (dart:isolate-patch/timer_impl.dart:398:19)
#16     _Timer._handleMessage (dart:isolate-patch/timer_impl.dart:429:5)
#17     _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:193:26)

I'm going for a walk and I'll come back to figure something out.

[gaaclarke]

Turns out the CI bot runs the tests differently than how it is documented they should be run locally. I've removed the x factor from the test and should pass in both places now.

[auto-submit]

auto label is removed for flutter/engine, pr: 37433, due to - The status or check suite Linux Unopt has failed. Please fix the issues identified (or deflake) before re-applying this label.

[gaaclarke]

oh my god, how many walls am I going to run into... fixed the format error

[flutter-dashboard]

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Changes reported for pull request #37433 at sha 5a77b8a

[gaaclarke]

I'm landing, ignoring the flutter-gold check. There is no way the changes are related. I've notified the team and flutter gold expert.