[libc++] Add missing include in exception_ptr.h

Windows builds were failing due to missing include for std::addressof
after D145095.

Differential revision: https://reviews.llvm.org/D145919

Author: zmodem

libcxx/include/__exception/exception_ptr.h

@@ -11,6 +11,7 @@
 
 #include <__config>
 #include <__exception/operations.h>
+#include <__memory/addressof.h>
 #include <cstddef>
 #include <cstdlib>