[mono][tasks] reduce large allocations in build tasks

[lewing]

It's late on a Friday so it is likely I'm missing something, but the hash comparison doesn't appear to be useful at all, that said I will assume it is useful and preserve the original behavior for now.

Use two rolling buffers to do file equality comparison since Read can return less than a full buffer, only advance a buffer once it is consumed, and compare the overlapping region.

Copilot reviewed 1 out of 1 changed files in this pull request and generated no comments.

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src/tasks/Common/Utils.cs:217

• Ensure that the new behavior introduced by the CompareFiles method is covered by tests. This includes scenarios where files are identical and where they differ.

private static bool CompareFiles(string filePath1, string filePath2)

[Copilot]

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

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src/tasks/Common/Utils.cs:270

• Ensure that the new behavior in CopyIfDifferent using ContentEqual is covered by tests.

bool areDifferent = !File.Exists(dst) || !ContentEqual(src, dst);

[lewing]

I'm certain there is a difference between the text comparison and bytewise comparison but I think any value is likely an artifact of history that no longer applies. I'm happy to remove the setting at the callers and will unless someone objects.

[lewing]

/ba-g issue files for red BA