Remove StatInterop.cs - unused P/Invoke to private runtime library

[Copilot]

The SDK was P/Invoking into System.Native (via libSystem.Native), a private implementation detail of the runtime. This caused breakage in .NET 7 on arm64 when the runtime changed the native function signature (dotnet/runtime#72308).

Changes

• Removed src/Cli/dotnet/StatInterop.cs - contained DllImport declarations for SystemNative_LStat and associated structs (FileStatus, Permissions, FileStatusFlags)

The file had no references in the codebase and was not being used. Originally intended for checking file ownership in SudoEnvironmentDirectoryOverride.cs, but that code path was never implemented.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Don't DllImport System.Native libraries</issue_title>
<issue_description>### Describe the bug
Today we are p/invoking into the System.Native library in dotnet/runtime to use the lstat function:

sdk/src/Cli/dotnet/StatInterop.cs

Lines 70 to 71 in 4536ed2

	[DllImport("libSystem.Native", EntryPoint = "SystemNative_LStat", SetLastError = true)]
	internal static extern int LStat(string path, out FileStatus output);

This isn't recommended because this library is a private implementation detail of the runtime. We should find another way to implement the required functionality here.

One possibility is to add the necessary APIs to .NET to read the current owner of a file:

sdk/src/Cli/dotnet/SudoEnvironmentDirectoryOverride.cs

Lines 111 to 135 in 4536ed2

	private static bool TempHomeIsOnlyRootWritable(string path)
	{
	if (StatInterop.LStat(path, out StatInterop.FileStatus fileStat) != 0)
	{
	return false;
	}
	return IsOwnedByRoot(fileStat) && GroupCannotWrite(fileStat) &&
	OtherUserCannotWrite(fileStat);
	}
	private static bool OtherUserCannotWrite(StatInterop.FileStatus fileStat)
	{
	return (fileStat.Mode & (int) StatInterop.Permissions.S_IWOTH) == 0;
	}
	private static bool GroupCannotWrite(StatInterop.FileStatus fileStat)
	{
	return (fileStat.Mode & (int) StatInterop.Permissions.S_IWGRP) == 0;
	}
	private static bool IsOwnedByRoot(StatInterop.FileStatus fileStat)
	{
	return fileStat.Uid == 0;
	}

.NET 7 added APIs to check the file's mode, but this code also needs to check the file's owner.

To Reproduce

This is the root cause of dotnet/runtime#72308. In .NET 7 the runtime changed the signature of this native function and broke the SDK on arm64.
</issue_description>

<agent_instructions>Remove the entire StatInterop.cs file as we do not think it is used or needed.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Don't DllImport System.Native libraries #26919

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[marcpopMSFT]

No testing done as we're just removing a file we don't think is used and would expect it to fail to build/run if still in use.

[Copilot]

Pull Request Overview

This PR removes an unused file that contained P/Invoke declarations to a private runtime library, preventing potential future breakage. The SDK was incorrectly depending on System.Native (via libSystem.Native), which is a private implementation detail of the runtime and caused breaking changes in .NET 7 on arm64.

• Removed src/Cli/dotnet/StatInterop.cs containing unused DllImport declarations for SystemNative_LStat and associated structs

[MiYanni]

Internal and doesn't seem to be referenced. Any chance copilot could do this kind of investigation repo-wide?