object-store: add missing include

Signed-off-by: NJonathan Tan <jonathantanmy@google.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

object-store.h

@@ -2,6 +2,9 @@
 #define OBJECT_STORE_H
 
 #include "oidmap.h"
+#include "list.h"
+#include "sha1-array.h"
+#include "strbuf.h"
 
 struct alternate_object_database {
 	struct alternate_object_database *next;