Make DEFINE_GLOBAL C++17 compliant.

The pointer to an object is not interconvertible with the pointer to its underlying storage,
and GCC raises a Wstrict-aliasing warning about UB resulting from the dereference.
(This is really a pointer provenance issue, not a type aliasing issue, as the underlying
void*[] is never actually directly used)
Additionally, void* potentially has a too-small alignment for some types (eg. long double).

We fix the fist issue by memory laundering, and the second by switching to aligned_storage_t.

--- src/third_party/blink/renderer/platform/wtf/static_constructors.h.old	2022-10-20 19:00:30.237477900 +0200
+++ src/third_party/blink/renderer/platform/wtf/static_constructors.h	2022-10-29 21:48:44.336995700 +0200
@@ -21,8 +21,11 @@
 #ifndef THIRD_PARTY_BLINK_RENDERER_PLATFORM_WTF_STATIC_CONSTRUCTORS_H_
 #define THIRD_PARTY_BLINK_RENDERER_PLATFORM_WTF_STATIC_CONSTRUCTORS_H_
 
+#include <new>
+#include <type_traits>
+
 // We need to avoid having static constructors. This is accomplished by defining
-// a static array of the appropriate size and alignment, and defining a const
+// a buffer of the appropriate size and alignment, and defining a const
 // reference that points to the buffer. During initialization, the object will
 // be constructed with placement new into the buffer. This works with MSVC, GCC,
 // and Clang without producing dynamic initialization code even at -O0. The only
@@ -33,7 +36,7 @@
 // Use an array of pointers instead of an array of char in case there is some
 // alignment issue.
 #define DEFINE_GLOBAL(type, name)                                          \
-  void* name##Storage[(sizeof(type) + sizeof(void*) - 1) / sizeof(void*)]; \
-  const type& name = *reinterpret_cast<type*>(&name##Storage)
+  std::aligned_storage_t<sizeof(type), alignof(type)> name##Storage; \
+  const type& name = *std::launder(reinterpret_cast<type*>(&name##Storage))
 
 #endif  // THIRD_PARTY_BLINK_RENDERER_PLATFORM_WTF_STATIC_CONSTRUCTORS_H_