Trivial C++23 fixes.

More "include what you use" stuff.

Change-Id: I3de72c6ede6f7d53756276232e7304429e610235
diff --git a/libc/malloc_debug/LogAllocatorStats.cpp b/libc/malloc_debug/LogAllocatorStats.cpp
index ee6bfdf..6ba505e 100644
--- a/libc/malloc_debug/LogAllocatorStats.cpp
+++ b/libc/malloc_debug/LogAllocatorStats.cpp
@@ -31,6 +31,8 @@
 #include <signal.h>
 #include <unistd.h>
 
+#include <atomic>
+
 #include "Config.h"
 #include "LogAllocatorStats.h"
 #include "debug_log.h"