vector: include missing header

`std::alignment_of` is in `type_traits`, so it needs to be included.
Fixes a compile error with xcode when compiling in c++23.

Author: timblechmann

common/sys/vector.h

@@ -5,6 +5,7 @@
 
 #include "alloc.h"
 #include <algorithm>
+#include <type_traits>
 
 namespace embree
 {