[libc++][NFC] Use std::malloc and std::free instead of unqualified versions in tests

[Mordante]

Nice! LGTM!

libcxx/test/std/utilities/memory/util.smartptr/util.smartptr.shared/util.smartptr.shared.create/make_shared_for_overwrite.pass.cpp

 // template<class T>
 //   shared_ptr<T> make_shared_for_overwrite(); // T is not U[]
 //
 // template<class T>
 //   shared_ptr<T> make_shared_for_overwrite(size_t N); // T is U[]
 
 #include <cassert>
 #include <concepts>
+#include <cstdlib>
 #include <cstring>
 #include <memory>
-#include <stdlib.h>
 #include <utility>
 
 #include "test_macros.h"
 
 template <class T, class... Args>
 concept HasMakeSharedForOverwrite =
     requires(Args&&... args) { std::make_shared_for_overwrite<T>(std::forward<Args>(args)...); };
 

 static_assert(!HasMakeSharedForOverwrite<int[]>);
 static_assert(!HasMakeSharedForOverwrite<Foo[]>);
 static_assert(!HasMakeSharedForOverwrite<int[], size_t, int>);
 static_assert(!HasMakeSharedForOverwrite<Foo[], size_t, int>);
 
 constexpr char pattern = 0xDE;
 
 void* operator new(std::size_t count) {
-  void* ptr = malloc(count);
+  void* ptr = std::malloc(count);
   for (std::size_t i = 0; i < count; ++i) {
     *(reinterpret_cast<char*>(ptr) + i) = pattern;
   }
   return ptr;
 }
 
 void* operator new[](std::size_t count) { return ::operator new(count); }
 
-void operator delete(void* ptr) noexcept { free(ptr); }
+void operator delete(void* ptr) noexcept { std::free(ptr); }
 
 void operator delete[](void* ptr) noexcept { ::operator delete(ptr); }
 
 struct WithDefaultConstructor {
   int i;
   constexpr WithDefaultConstructor() : i(5) {}
 };
 

libcxx/test/std/utilities/smartptr/unique.ptr/unique.ptr.create/make_unique_for_overwrite.default_init.pass.cpp

 // template<class T>
 //   constexpr unique_ptr<T> make_unique_for_overwrite(size_t n); // T is U[]
 
 // Test the object is not value initialized
 
 #include <cassert>
 #include <concepts>
 #include <cstddef>
+#include <cstdlib>
 #include <memory>
-#include <stdlib.h>
 
 constexpr char pattern = 0xDE;
 
 void* operator new(std::size_t count) {
-  void* ptr = malloc(count);
+  void* ptr = std::malloc(count);
   for (std::size_t i = 0; i < count; ++i) {
     *(reinterpret_cast<char*>(ptr) + i) = pattern;
   }
   return ptr;
 }
 
 void* operator new[](std::size_t count) { return ::operator new(count); }
 
-void operator delete(void* ptr) noexcept { free(ptr); }
+void operator delete(void* ptr) noexcept { std::free(ptr); }
 
 void operator delete[](void* ptr) noexcept { ::operator delete(ptr); }
 
 void test() {
   {
     std::same_as<std::unique_ptr<int>> auto ptr = std::make_unique_for_overwrite<int>();
     assert(*(reinterpret_cast<char*>(ptr.get())) == pattern);
   }