Add missing <sys/file.h> include for flock.

Change-Id: I5c9bb4aa74d8a36d44e086bbcb5d60876727ce4c
diff --git a/cmds/installd/commands.c b/cmds/installd/commands.c
index 3b09aa7..386d2f3 100644
--- a/cmds/installd/commands.c
+++ b/cmds/installd/commands.c
@@ -16,6 +16,7 @@
 
 #include <inttypes.h>
 #include <sys/capability.h>
+#include <sys/file.h>
 #include "installd.h"
 #include <cutils/sched_policy.h>
 #include <diskusage/dirsize.h>