Add missing includes.

Change-Id: Ibf549266a19a67eb9158d341a69dddfb654be669
diff --git a/libc/bionic/debug_stacktrace.cpp b/libc/bionic/debug_stacktrace.cpp
index 7d3c76e..c6ce714 100644
--- a/libc/bionic/debug_stacktrace.cpp
+++ b/libc/bionic/debug_stacktrace.cpp
@@ -30,6 +30,7 @@
 
 #include <dlfcn.h>
 #include <inttypes.h>
+#include <malloc.h>
 #include <unistd.h>
 #include <unwind.h>
 #include <sys/types.h>