zipalign missing header

Remove assumptions about header side effects

Test: compile
Bug: 30465923
Change-Id: I117567b0f99814b9d9a955b39c56f43f7972cf62
diff --git a/tools/zipalign/ZipAlign.cpp b/tools/zipalign/ZipAlign.cpp
index aef91a5..d56ac29 100644
--- a/tools/zipalign/ZipAlign.cpp
+++ b/tools/zipalign/ZipAlign.cpp
@@ -19,8 +19,9 @@
  */
 #include "ZipFile.h"
 
-#include <stdlib.h>
 #include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
 
 using namespace android;