tweak alignment fix to __cxa_exception replica under libstdc++

Summary: Best to use `[[gnu::aligned]]` exactly since that is precisely what libstdc++ uses internally. Attempting to use `max_align_t` instead is an approximation but may not work exactly.

Reviewed By: skrueger

Differential Revision: D68520433

fbshipit-source-id: c74e41b6ab576838b06ee4db87230e9a86b90c09

third-party/folly/src/folly/lang/Exception.cpp

@@ -104,7 +104,11 @@ namespace __cxxabiv1 {
 static constexpr size_t __folly_unwind_exception_align = 8;
 #else
 //  https://github.com/gcc-mirror/gcc/blob/releases/gcc-14.2.0/libgcc/unwind-generic.h#L106
-static constexpr size_t __folly_unwind_exception_align = alignof(max_align_t);
+struct __folly_unwind_exception_align_t {
+  [[gnu::aligned]] int data;
+};
+static constexpr size_t __folly_unwind_exception_align =
+    alignof(__folly_unwind_exception_align_t);
 #endif
 
 static constexpr uint64_t __gxx_primary_exception_class =