vold should #include <sys/sysmacros.h>

Bug: https://github.com/android-ndk/ndk/issues/398
Test: builds
Change-Id: I7a1ca1701099886fb493cc5288d6ee867d5f520a
diff --git a/PrivateVolume.cpp b/PrivateVolume.cpp
index e5809fb..e66e04d 100644
--- a/PrivateVolume.cpp
+++ b/PrivateVolume.cpp
@@ -33,6 +33,7 @@
 #include <sys/mount.h>
 #include <sys/stat.h>
 #include <sys/types.h>
+#include <sys/sysmacros.h>
 #include <sys/wait.h>
 #include <sys/param.h>