<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/87373>87373</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Backport libc++ stddef fix for `__need_` macros added in LLVM 18
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            libc++
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          ian-twilightcoder
      </td>
    </tr>
</table>

<pre>
    We should backport https://github.com/llvm/llvm-project/pull/86843 because it fixes interactions with the `__need_` macros that were added in clang in LLVM 18.

/cherry-pick 2950283dddab03c183c1be2d7de9d4999cc86131
</pre>
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