It worked on the Mac version of Powershell (`pwsh`) but [not on the
Windows
bots](https://logs.chromium.org/logs/flutter/buildbucket/cr-buildbucket/8709168939844960513/+/u/run_test.dart_for_framework_tests_shard_and_subshard_misc/stdout):
```txt
00:09 +37 ~2 -3: C:/b/s/w/ir/x/w/flutter/dev/tools/test/last_engine_commit_test.dart: returns the last engine commit [E]
Failed running "powershell [C:\b\s\w\ir\x\t\last_engine_commit_test.88f44c9f\flutter\bin\internal\last_engine_commit.ps1]" (exit code = 1),
stdout:
stderr: Join-Path : A positional parameter cannot be found that accepts argument 'internal'.
At C:\b\s\w\ir\x\t\last_engine_commit_test.88f44c9f\flutter\bin\internal\last_engine_commit.ps1:29 char:35
+ ... SION_PATH = Join-Path $gitToplevel "bin" "internal" "release-candidat ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : InvalidArgument: (:) [Join-Path], ParentContainsErrorRecordException
+ FullyQualifiedErrorId : PositionalParameterNotFound,Microsoft.PowerShell.Commands.JoinPathCommand
```
... this looks safer, I'll make sure it passes pre-subs this time.
This fixes https://github.com/flutter/flutter/pull/172184 by considering
the last commit to `release-candidate-branch.version` as the significant
commit.
Otherwise, operationally, it works the same. I tested this on 3.35 and
it works as expected (where the current does not).
