[xabt] Fix Windows long path directory removal

[jonathanpeppers]

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Visual Studio's .NET Framework MSBuild host can report XARDF7024 while deleting generated Java classes whose paths exceed MAX_PATH. The retry preserved the trailing directory separator from the MSBuild property, producing an extended path that .NET Framework rejects with ERROR_INVALID_NAME.

Normalize the directory path before retrying and make Files.ToLongPath() idempotent so repeated failures cannot add the \\?\ prefix more than once. Direct unit coverage verifies both the shared helper and consecutive RemoveDirFixed retries.

Fixes #12207

• Useful description of why the change is necessary.
• Links to issues fixed
• Unit tests

[Copilot]

Pull request overview

This PR fixes a Windows/.NET Framework MSBuild-host failure (XARDF7024) when RemoveDirFixed retries directory deletion using \\?\ long paths: trailing directory separators are now trimmed before applying the long-path prefix, and a unit test validates the normalized retry path.

Changes:

• Trim trailing directory separators before converting to \\?\ long paths on the Windows retry path.
• Route deletion through an injectable DeleteDirectory delegate to enable deterministic unit testing.
• Add a Windows-only unit test that forces the retry path and verifies the long-path retry uses a normalized directory path.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/Xamarin.Android.Build.Tasks/Tasks/RemoveDirFixed.cs	Normalizes retry paths before long-path prefixing; adds injectable delete hook for tests.
src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/Tasks/RemoveDirTests.cs	Adds coverage for trailing-separator long-path retry behavior on Windows.

[jonathanpeppers]

/review

[github-actions]

✅ Android PR Reviewer completed successfully!

[github-actions]

✅ LGTM

Clean, well-scoped fix for the Windows XARDF7024 / MAX_PATH directory-removal failure.

What the change does (verified against the full sources):

• Files.ToLongPath() is now idempotent — it won't add the \\?\ prefix twice. The StartsWith (LongPathPrefix, StringComparison.Ordinal) guard is correct (the prefix contains no alphabetic characters, so Ordinal is appropriate).
• RemoveDirFixed trims trailing directory separators before converting to a long path, matching the root cause: .NET Framework rejects \\?\ extended paths that end in a separator with ERROR_INVALID_NAME. TrimEnd correctly handles both DirectorySeparatorChar and AltDirectorySeparatorChar.
• The DeleteDirectory internal test seam is a reasonable, minimal way to simulate the failure without needing a real >260-char path.

Test coverage — good:

• ToLongPathIsIdempotent covers the shared helper directly.
• LongPathWithTrailingDirectorySeparator exercises consecutive RemoveDirFixed retries and asserts the trailing separator is stripped and the prefix is applied only once.

Notes:

• CI is still pending (no failures reported yet) — not blocking review.
• One low-priority inline observation about the long-path conversion consuming a retry attempt/delay; pre-existing and harmless at the default of 10 attempts.

Counts — ❌ 0 · ⚠️ 0 · 💡 1. Nice, focused fix with matching regression tests.

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