ecp: add back dummy ecp_curves_new.c for compat

Signed-off-by: Manuel Pégourié-Gonnard <[email protected]>

library/ecp_curves_new.c

@@ -0,0 +1,9 @@
+/*
+ *  This file used to be non-empty. It's kept only for compatibility
+ *  with custom build systems in LTS branches.
+ *
+ *  Copyright The Mbed TLS Contributors
+ *  SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
+ */
+
+typedef int iso_c_forbids_an_empty_translation_unit;