IWYU: mark <cstddef> as needed

Newer IWYU is not seeing them as needed for `size_t`.

Source/CPack/IFW/cmCPackIFWCommon.cxx

@@ -2,7 +2,7 @@
    file Copyright.txt or https://cmake.org/licensing for details.  */
 #include "cmCPackIFWCommon.h"
 
-#include <cstddef>
+#include <cstddef> // IWYU pragma: keep
 #include <sstream>
 #include <utility>
 #include <vector>

Source/CTest/cmCTestMultiProcessHandler.cxx

@@ -6,7 +6,7 @@
 #include <cassert>
 #include <chrono>
 #include <cmath>
-#include <cstddef>
+#include <cstddef> // IWYU pragma: keep
 #include <cstdlib>
 #include <cstring>
 #include <iomanip>

Source/CTest/cmCTestRunTest.cxx

@@ -3,7 +3,7 @@
 #include "cmCTestRunTest.h"
 
 #include <chrono>
-#include <cstddef>
+#include <cstddef> // IWYU pragma: keep
 #include <cstdint>
 #include <cstdio>
 #include <cstring>

Source/CTest/cmCTestTestHandler.cxx

@@ -5,7 +5,7 @@
 #include <algorithm>
 #include <chrono>
 #include <cmath>
-#include <cstddef>
+#include <cstddef> // IWYU pragma: keep
 #include <cstdio>
 #include <cstdlib>
 #include <cstring>

Source/bindexplib.cxx

@@ -64,7 +64,7 @@
  */
 #include "bindexplib.h"
 
-#include <cstddef>
+#include <cstddef> // IWYU pragma: keep
 #include <sstream>
 #include <vector>
 

Source/cmForEachCommand.cxx

@@ -4,7 +4,7 @@
 
 #include <algorithm>
 #include <cassert>
-#include <cstddef>
+#include <cstddef> // IWYU pragma: keep
 // NOTE The declaration of `std::abs` has moved to `cmath` since C++17
 // See https://en.cppreference.com/w/cpp/numeric/math/abs
 // ALERT But IWYU used to lint `#include`s do not "understand"

Source/cmStringAlgorithms.cxx

@@ -4,7 +4,7 @@
 
 #include <algorithm>
 #include <cerrno>
-#include <cstddef>
+#include <cstddef> // IWYU pragma: keep
 #include <cstdio>
 #include <cstdlib>
 

Source/cmUVProcessChain.h

@@ -4,7 +4,7 @@
 #define cmUVProcessChain_h
 
 #include <array>
-#include <cstddef>
+#include <cstddef> // IWYU pragma: keep
 #include <cstdint>
 #include <iosfwd>
 #include <memory>

Source/cmXMLWriter.h

@@ -6,7 +6,7 @@
 #include "cmConfigure.h" // IWYU pragma: keep
 
 #include <chrono>
-#include <cstddef>
+#include <cstddef> // IWYU pragma: keep
 #include <ctime>
 #include <ostream>
 #include <stack>

Tests/CMakeLib/testCTestBinPacker.cxx

@@ -1,4 +1,4 @@
-#include <cstddef>
+#include <cstddef> // IWYU pragma: keep
 #include <iostream>
 #include <map>
 #include <string>

Tests/CMakeLib/testGccDepfileReader.cxx

@@ -1,4 +1,4 @@
-#include <cstddef>
+#include <cstddef> // IWYU pragma: keep
 #include <iostream>
 #include <memory>
 #include <string>

Tests/RunCMake/CTestResourceAllocation/ctresalloc.cxx

@@ -1,6 +1,6 @@
 #include <cassert>
 #include <chrono>
-#include <cstddef>
+#include <cstddef> // IWYU pragma: keep
 #include <cstdlib>
 #include <iostream>
 #include <map>