captureStdErr

pub fn captureStdErr(run: *Run, options: CapturedStdIo.Options) std.Build.LazyPath {
    assert(run.stdio != .inherit);
    assert(run.stdio != .zig_test);

    const b = run.step.owner;
    const graph = b.graph;
    const arena = graph.arena;

    if (run.captured_stderr) |captured| return .{ .generated = .{ .index = captured.generated_file } };

    const captured = arena.create(CapturedStdIo) catch @panic("OOM");
    captured.* = .{
        .prefix = "",
        .basename = if (options.basename) |basename| graph.dupeString(basename) else "stderr",
        .generated_file = graph.addGeneratedFile(&run.step),
        .trim_whitespace = options.trim_whitespace,
    };
    run.captured_stderr = captured;
    return .{ .generated = .{ .index = captured.generated_file } };
}