Newer IWYU is not seeing this as necessary for `_GLIBCXX_USE_CXX11_ABI`.
@@ -1,7 +1,7 @@
/* Distributed under the OSI-approved BSD 3-Clause License. See accompanying
file Copyright.txt or https://cmake.org/licensing for details. */
-#include <cstddef>
+#include <cstddef> // IWYU pragma: keep
#include <cstring>
#include <iostream>
#include <iterator>