vold should #include <sys/sysmacros.h>

Bug: https://github.com/android-ndk/ndk/issues/398
Test: builds
Change-Id: I7a1ca1701099886fb493cc5288d6ee867d5f520a
diff --git a/Disk.cpp b/Disk.cpp
index 6562d96..cb9c9bb 100644
--- a/Disk.cpp
+++ b/Disk.cpp
@@ -35,6 +35,7 @@
 #include <stdlib.h>
 #include <sys/types.h>
 #include <sys/stat.h>
+#include <sys/sysmacros.h>
 #include <sys/mount.h>
 
 using android::base::ReadFileToString;