options: cast page_size to unsigned long for sprintf()

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/options.c b/options.c
index dd71f1e..84101d1 100644
--- a/options.c
+++ b/options.c
@@ -2493,7 +2493,7 @@
 	char buf[128];
 	long l;
 
-	sprintf(buf, "%lu", page_size);
+	sprintf(buf, "%lu", (unsigned long) page_size);
 	fio_keywords[0].replace = strdup(buf);
 
 	mb_memory = os_phys_mem() / (1024 * 1024);