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

Change-Id: I0c66c03aeb4df614f7880a830b95c40f43f804db
diff --git a/cmds/idmap/create.cpp b/cmds/idmap/create.cpp
index 7a501a4..16532b8 100644
--- a/cmds/idmap/create.cpp
+++ b/cmds/idmap/create.cpp
@@ -7,6 +7,7 @@
 #include <utils/String8.h>
 
 #include <fcntl.h>
+#include <sys/file.h>
 #include <sys/stat.h>
 
 using namespace android;