Support building fs_mgr against musl

Support building fs_mgr against musl by including the missing
sys/types.h header.

Bug: 190084016
Test: m USE_HOST_MUSL=true host-native
Change-Id: Ie3b3907b1c60ba550c04e8780f11b7adf09a6471

Author: colincross

fs_mgr/libdm/include/libdm/dm.h

@@ -24,6 +24,7 @@
 #include <linux/types.h>
 #include <stdint.h>
 #include <sys/sysmacros.h>
+#include <sys/types.h>
 #include <unistd.h>
 
 #include <chrono>