Add missing include

tests/perfmodels/user_base.c

@@ -16,6 +16,7 @@
 
 #include <starpu.h>
 #include <starpu_scheduler.h>
+#include <unistd.h>
 #include "../helper.h"
 
 /*

tests/perfmodels/valid_model.c

@@ -17,6 +17,7 @@
 
 #include <starpu.h>
 #include <core/perfmodel/perfmodel.h>
+#include <unistd.h>
 #include "../helper.h"
 
 /*