stmhal: Update for static mod sys.
diff --git a/unix/mpconfigport.h b/unix/mpconfigport.h
index e2f2a69..832bdb0 100644
--- a/unix/mpconfigport.h
+++ b/unix/mpconfigport.h
@@ -13,6 +13,7 @@
 #define MICROPY_FLOAT_IMPL          (MICROPY_FLOAT_IMPL_DOUBLE)
 #define MICROPY_LONGINT_IMPL        (MICROPY_LONGINT_IMPL_MPZ)
 #define MICROPY_PATH_MAX            (PATH_MAX)
+#define MICROPY_MOD_SYS_STDFILES    (1)
 
 // type definitions for the specific machine