[mmitche]

Capture Windows local validation build binlogs

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Preserve MSBuild logs from Windows local validation builds.

Description

Enable binary logging for the No NodeJS, Debug, and Release build steps in the public, official, and unofficial Windows local-validation jobs. The jobs intentionally run without -ci, so the build script does not otherwise enable its default binlogger. The existing attempt-specific artifact upload already runs after a failed step.

Each MSBuild invocation uses a unique, step-specific filename under artifacts/log/. This preserves both native and managed build logs without later steps overwriting them. The quoted {} placeholder is passed through the PowerShell wrapper to MSBuild's unique-name expansion.

This is a diagnostic change, not a fix for the file lock. A future binlog can help identify overlapping targets or producers; a separate handle trace may still be needed to identify the process holding a file. Logging adds build I/O and artifact size, but is limited to this validation job and does not add retries or change failure handling.

Validation

• python .\check.py green (session-only Windows harness, with the repository environment activated and the workspace and system dotnet.exe configured): passed 27 cases. It exercised the actual eng/build.ps1 and eng/build.cmd entry points with a small injected MSBuild project. Across all three pipeline definitions, 18 native/managed failure scenarios generated distinct binlogs, and nine successful build steps preserved earlier logs. The corresponding 18 scenarios reproduced the missing artifact before the change.
• A local Windows file-lock reproduction failed with MSB3491. The baseline left the artifact directory without a binlog; the changed Release command retained separate native and managed binlogs, and the managed binlog contained the file-lock error.
• git -c core.longpaths=true diff --check: passed.
• Not run: the real Static Web Assets/QuickGrid build, the repository's .NET 12 alpha SDK, Visual Studio desktop MSBuild, or an Azure Pipelines hosted job/artifact upload. The local harness used an installed system .NET MSBuild with an injected project; it does not verify the original flake or the hosted upload service.

Relates to #31.